START-INFO-DIR-ENTRY * mysql: (mysql). *MySQL* documentation. END-INFO-DIR-ENTRY This is a manual for *MySQL*. This version is about the 3.23.39 version of *MySQL*. You can find a manual about any older version of *MySQL* in the binary or source distribution for that version. General Information About MySQL ******************************* This is the *MySQL* reference manual; it documents *MySQL* Version 3.23.39. As *MySQL* is work in progress, the manual gets updated frequently. There is a very good chance that this version is out of date, unless you are looking at it online. The most recent version of this manual is available at `http://www.mysql.com/documentation/' in many different formats. If you have a hard time finding information in the manual, you can try the searchable PHP version at `http://www.mysql.com/documentation/manual.php'. *MySQL* is a very fast, multi-threaded, multi-user, and robust SQL (Structured Query Language) database server. *MySQL* is free software. It is licensed with the *GNU GENERAL PUBLIC LICENSE* `http://www.gnu.org/'. *Note Licensing and Support::. The *MySQL* home page (http://www.mysql.com/) provides the latest information about *MySQL*. The following list describes some useful sections of the manual: * For information about the company behind *MySQL*, see *Note What is MySQL AB::. * For a discussion of *MySQL*'s capabilities, see *Note Features::. * For installation instructions, see *Note Installing::. * For tips on porting *MySQL* to new architectures or operating systems, see *Note Porting::. * For information about upgrading from a Version 3.22 release, see *Note Upgrading-from-3.22::. * For a tutorial introduction to *MySQL*, see *Note Tutorial::. * For examples of SQL and benchmarking information, see the benchmarking directory (`sql-bench' in the distribution). * For a history of new features and bug fixes, see *Note News::. * For a list of currently known bugs and misfeatures, see *Note Bugs::. * For future plans, see *Note TODO::. * For a list of all the contributors to this project, see *Note Credits::. *IMPORTANT:* Reports of errors (often called bugs), as well as questions and comments, should be sent to the mailing list at . *Note Bug reports::. The `mysqlbug' script should be used to generate bug reports. For source distributions, the `mysqlbug' script can be found in the `scripts' directory. For binary distributions, `mysqlbug' can be found in the `bin' directory. If you have found a sensitive security bug in *MySQL*, you should send an email to . If you have any suggestions concerning additions or corrections to this manual, please send them to the manual team at . This is a reference manual; it does not provide general instruction on SQL or relational database concepts. If you want general information about SQL, see *Note General-SQL::. For books that focus more specifically on *MySQL*, see *Note MySQL-Books::. What Is MySQL ============= *MySQL*, the most popular Open Source SQL database, is provided by *MySQL AB*. *MySQL AB* is a commercial company that builds its business providing services around the *MySQL* database. *Note What is MySQL AB::. *MySQL* is a database management system. A database is a structured collection of data. It may be anything from a simple shopping list to a picture gallery or the vast amounts of information in a corporate network. To add, access, and process data stored in a computer database, you need a database management system such as *MySQL*. Since computers are very good at handling large amounts of data, database management plays a central role in computing, as stand-alone utilities, or as parts of other applications. *MySQL* is a relational database management system. A relational database stores data in separate tables rather than putting all the data in one big storeroom. This adds speed and flexibility. The tables are linked by defined relations making it possible to combine data from several tables on request. The SQL part of *MySQL* stands for "Structured Query Language" - the most common standardized language used to access databases. *MySQL* is Open Source Software. Open Source means that it is possible for anyone to use and modify. Anybody can download *MySQL* from the Internet and use it without paying anything. Anybody so inclined can study the source code and change it to fit their needs. *MySQL* uses the GPL (GNU General Public License) `http://www.gnu.org', to define what you may and may not do with the software in different situations. If you feel uncomfortable with the GPL or need to embed *MySQL* into a commercial application you can buy a commercially licensed version from us. Why use *MySQL*? *MySQL* is very fast, reliable, and easy to use. If that is what you are looking for, you should give it a try. *MySQL* also has a very practical set of features developed in very close cooperation with our users. You can find a performance comparison of *MySQL* to some other database managers on our benchmark page. *Note Benchmarks::. *MySQL* was originally developed to handle very large databases much faster than existing solutions and has been successfully used in highly demanding production environments for several years. Though under constant development, *MySQL* today offers a rich and very useful set of functions. The connectivity, speed, and security make *MySQL* highly suited for accessing databases on the Internet. The technical features of *MySQL* For advanced technical information, see *Note Reference::. *MySQL* is a client/server system that consists of a multi-threaded SQL server that supports different backends, several different client programs and libraries, administrative tools, and several programming interfaces. We also provide *MySQL* as a multi-threaded library which you can link into your application to get a smaller, faster, easier to manage product. *MySQL* has a lot of contributed software available. It is very likely that you will find that your favorite application or language already supports *MySQL*. The official way to pronounce *MySQL* is "My Ess Que Ell" (not MY-SEQUEL). But we try to avoid correcting people who say MY-SEQUEL. What Is MySQL AB ================ *MySQL AB* is the Swedish company owned and run by the *MySQL* founders and main developers. We are dedicated to developing *MySQL* and spreading our database to new users. *MySQL AB* owns the copyright to the *MySQL* server source code and the *MySQL* trademark. A significant amount of revenues from our services goes to developing *MySQL*. *Note What-is::. *MySQL AB* has been profitable providing *MySQL* from the start. We don't get any outside funding, but have earned all our money ourselves. We are searching after partners that would like to support our development of *MySQL* so that we could accelerate the development pace. If you are interested in doing this, you can email about this! *MySQL AB* has currently 20+ people on its payroll and is growing rapidly. `http://www.mysql.com/development/team.html'. Our main sources of income are: * Commercial high quality support for *MySQL* provided by the *MySQL* developers themselves. If you are interested in purchasing a support contract, please visit `https://order.mysql.com/' to view our support options or to order support. * Consulting services. We have developers and consultants in 12 countries and partners in many other countries that can help you with almost any *MySQL* related issues. If you need consulting services, please email a good description of your needs to ! If we can't handle this ourselves we can usually find a partner or a developer that can help you with your problems. * We sell licenses for using *MySQL* as an embedded database. *Note Cost::. If you have a commercial product for which you need a fast, high quality database, but you can't afford to make your product Open Source, you can buy the right to use the *MySQL* server under a normal commercial copyright. If you are interested in this you can buy *MySQL* licenses at `https://order.mysql.com/' or contact us at . * Advertising. `http://www.mysql.com/' is a very popular web site with more than 10,000,000 page views per months (January 2001). By putting a banner on this you are guaranteed to reach a lot of potential customers in the Open source, Linux and database community. If you are interested in this email . * We are building a partner program to be able to provide *MySQL* services in every country. If you are interested in becoming a partner of *MySQL AB* please visit `http://www.mysql.com/information/partners.html' or email . * We provide *MySQL* training through our partner programs. For more information, please email . * The *MySQL* brand has, since 1995, been associated with speed and reliability, and is known to be something you can depend upon. If you are interested in using the *MySQL* trademark in your marketing, you can email about this. The *MySQL* core values show our dedication to *MySQL* and Open Source. We want *MySQL* to be: * The best and the most used database in the world. * Available and affordable for all. * Easy to use. * Continuously improved while remaining fast and safe. * Fun to use and improve. * Free from bugs. *MySQL AB* and the people of *MySQL AB*: * Promote Open Source Philosophy and support the Open Source Community. * Aim to be good citizens. * Prefer partners that share our values and mind-set. * Answer mail and give support. * Are a virtual company, networking with others. * Work against software patents. About This Manual ================= This manual is currently available in Texinfo, plain text, Info, HTML, PostScript, and PDF versions. The primary document is the Texinfo file. The HTML version is produced automatically using a modified version of `texi2html'. The plain text and Info versions are produced with `makeinfo'. The Postscript version is produced using `texi2dvi' and `dvips'. The PDF version is produced with `pdftex'. This manual is written and maintained by David Axmark, Michael (Monty) Widenius, Jeremy Cole, and Paul DuBois. For other contributors, see *Note Credits::. Conventions Used in This Manual ------------------------------- This manual uses certain typographical conventions: `constant' Constant-width font is used for command names and options; SQL statements; database, table and column names; C and Perl code; and environment variables. Example: "To see how `mysqladmin' works, invoke it with the `--help' option." `filename' Constant-width font with surrounding quotes is used for filenames and pathnames. Example: "The distribution is installed under the `/usr/local/' directory." `c' Constant-width font with surrounding quotes is also used to indicate character sequences. Example: "To specify a wild card, use the `%' character." _italic_ Italic font is used for emphasis, _like this_. *boldface* Boldface font is used for access privilege names (for example, "do not grant the *process* privilege lightly") and occasionally to convey *especially strong emphasis*. When commands are shown that are meant to be executed by a particular program, the program is indicated by a prompt shown before the command. For example, `shell>' indicates a command that you execute from your login shell, and `mysql>' indicates a command that you execute from the `mysql' client program: shell> type a shell command here mysql> type a mysql command here Shell commands are shown using Bourne shell syntax. If you are using a `csh'-style shell, you may need to issue commands slightly differently. For example, the sequence to set an environment variable and run a command looks like this in Bourne shell syntax: shell> VARNAME=value some_command For `csh', you would execute the sequence like this: shell> setenv VARNAME value shell> some_command Often, database, table, and column names must be substituted into commands. To indicate that such substitution is necessary, this manual uses `db_name', `tbl_name' and `col_name'. For example, you might see a statement like this: mysql> SELECT col_name FROM db_name.tbl_name; This means that if you were to enter a similar statement, you would supply your own database, table, and column names, perhaps like this: mysql> SELECT author_name FROM biblio_db.author_list; SQL statements may be written in uppercase or lowercase. When this manual shows a SQL statement, uppercase is used for particular keywords if those keywords are under discussion (to emphasize them) and lowercase is used for the rest of the statement. For example, you might see the following in a discussion of the `SELECT' statement: mysql> SELECT count(*) FROM tbl_name; On the other hand, in a discussion of the `COUNT()' function, the same statement would be written like this: mysql> select COUNT(*) from tbl_name; If no particular emphasis is intended, all keywords are written uniformly in uppercase. In syntax descriptions, square brackets (`[' and `]') are used to indicate optional words or clauses: DROP TABLE [IF EXISTS] tbl_name When a syntax element consists of a number of alternatives, the alternatives are separated by vertical bars (`|'). When one member from a set of choices *may* be chosen, the alternatives are listed within square brackets (`[' and `]'): TRIM([[BOTH | LEADING | TRAILING] [remstr] FROM] str) When one member from a set of choices *must* be chosen, the alternatives are listed within braces (`{' and `}'): {DESCRIBE | DESC} tbl_name {col_name | wild} History of MySQL ================ We once started out with the intention of using `mSQL' to connect to our tables using our own fast low-level (ISAM) routines. However, after some testing we came to the conclusion that `mSQL' was not fast enough nor flexible enough for our needs. This resulted in a new SQL interface to our database but with almost the same API interface as `mSQL'. This API was chosen to ease porting of third-party code. The derivation of the name *MySQL* is not perfectly clear. Our base directory and a large number of our libraries and tools have had the prefix "my" for well over 10 years. However, Monty's daughter (some years younger) is also named My. Which of the two gave its name to *MySQL* is still a mystery, even for us. Books About MySQL ================= While this manual is still the right place for up to date technical information, its primary goal is to contain everything there is to know about *MySQL*. It is sometimes nice to have a bound book to read in bed or while you travel. Here is a list of books about *MySQL* and related subjects (in English). By purchasing a book through these hyperlinks provided herein, you are contributing to the development of *MySQL*. _MySQL_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0735709211&bfmtype=book) Publisher New Riders Author Paul DuBois Pub Date 1st Edition December 1999 ISBN 0735709211 Pages 800 Price $49.99 US Downloadable examples `samp_db' distribution (http://www.kitebird.com/mysql-book/) Errata are available here (http://www.kitebird.com/mysql-book/errata.html) Foreword by Michael "Monty" Widenius, *MySQL* Moderator. In _MySQL_, Paul DuBois provides you with a comprehensive guide to one of the most popular relational database systems. Paul has contributed to the online documentation for *MySQL* and is an active member of the *MySQL* community. The principal *MySQL* developer, Monty Widenius, and a network of his fellow developers reviewed the manuscript, and provided Paul with the kind of insight no one else could supply. Instead of merely giving you a general overview of *MySQL*, Paul teaches you how to make the most of its capabilities. Through two sample database applications that run throughout the book, he gives you solutions to problems you're sure to face. He helps you integrate *MySQL* efficiently with third-party tools, such as PHP and Perl, enabling you to generate dynamic Web pages through database queries. He teaches you to write programs that access *MySQL* databases, and also provides a comprehensive set of references to column types, operators, functions, SQL syntax, *MySQL* programming, C API, Perl `DBI', and PHP API. _MySQL_ simply gives you the kind of information you won't find anywhere else. If you use *MySQL*, this book provides you with: * An introduction to *MySQL* and SQL. * Coverage of *MySQL*'s data types and how to use them. * Thorough treatment of how to write client programs in C. * A guide to using the Perl `DBI' and PHP APIs for developing command-line and Web-based applications. * Tips on administrative issues such as user accounts, backup, crash recovery, and security. * Help in choosing an ISP for *MySQL* access. * A comprehensive reference for *MySQL*'s data types, operators, functions, and SQL statements and utilities. * Complete reference guides for *MySQL*'s C API, the Perl `DBI' API, and PHP's *MySQL*-related functions. _MySQL & mSQL_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=1565924347&bfmtype=book) Publisher O'Reilly Authors Randy Jay Yarger, George Reese & Tim King Pub Date 1st Edition July 1999 ISBN 1-56592-434-7, Order Number: 4347 Pages 506 Price $34.95 This book teaches you how to use *MySQL* and `mSQL', two popular and robust database products that support key subsets of SQL on both Linux and Unix systems. Anyone who knows basic C, Java, Perl, or Python can write a program to interact with a database, either as a stand-alone application or through a Web page. This book takes you through the whole process, from installation and configuration to programming interfaces and basic administration. Includes plenty of tutorial material. _Sams' Teach Yourself MySQL in 21 Days_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0672319144&bfmtype=book) Publisher Sams Authors Mark Maslakowski and Tony Butcher Pub Date June 2000 ISBN 0672319144 Pages 650 Price $39.99 Sams' _Teach Yourself MySQL in 21 Days_ is for intermediate Linux users who want to move into databases. A large share of the audience is Web developers who need a database to store large amounts of information that can be retrieved via the Web. Sams' _Teach Yourself MySQL in 21 Days_ is a practical, step-by-step tutorial. The reader will learn to design and employ this open source database technology into his or her Web site using practical, hands-on examples to follow. _E-Commerce Solutions with MySQL_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0761524452&bfmtype=book) Publisher Prima Communications, Inc. Authors N/A Pub Date January 2000 ISBN 0761524452 Pages 500 Price $39.99 No description available. _MySQL and PHP from Scratch_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0789724405&bfmtype=book) Publisher Que Authors N/A Pub Date September 2000 ISBN 0789724405 Pages 550 Price $34.99 This book puts together information on installing, setting up, and troubleshooting Apache, *MySQL*, PHP3, and IMP into one complete volume. You also learn how each piece is part of a whole by learning, step-by-step, how to create a web-based e-mail system. Learn to run the equivalent of Active Server Pages (ASP) using PHP3, set up an e-commerce site using a database and the Apache web server, and create a data entry system (such as sales, product quality tracking, customer preferences, etc) that no installation in the PC. _Professional MySQL Programming_ Available Barnes and Noble (http://shop.barnesandnoble.com/bookSearch/isbnInquiry.asp?isbn=1861005164) Publisher Wrox Press, Inc. Authors N/A Pub Date Late 2001 ISBN 1861005164 Pages 1000 Price $49.99 No description available. _Professional Linux Programming_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=1861003013&bfmtype=book) Publisher Wrox Press, Inc. Authors N/A Pub Date September 2000 ISBN 1861003013 Pages 1155 Price $47.99 In this follow-up to the best-selling _Beginning Linux Programming_, you will learn from the authors' real-world knowledge and experience of developing software for Linux; you'll be taken through the development of a sample 'DVD Store' application, with 'theme' chapters addressing different aspects of its implementation. Meanwhile, individual "take-a-break" chapters cover important topics that go beyond the bounds of the central theme. All focus on the practical aspects of programming, showing how crucial it is to choose the right tools for the job, use them as they should be used, and get things right first time. _PHP and MySQL Web Development_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0672317842&bfmtype=book) Publisher Sams Authors Luke Welling, Laura Thomson Pub Date March 2001 ISBN 0672317842 Pages 700 Price $49.99 _PHP and MySQL Web Development_ introduces you to the advantages of implementing both *MySQL* and PHP. These advantages are detailed through the provision of both statistics and several case studies. A practical web application is developed throughout the book, providing you with the tools necessary to implement a functional online database. Each function is developed separately, allowing you the choice to incorporate only those parts that you would like to implement. Programming concepts of the PHP language are highlighted, including functions which tie *MySQL* support into a PHP script and advanced topics regarding table manipulation. *Books recommended by the MySQL Developers* _SQL-99 Complete, Really_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0879305681&bfmtype=book) Publisher CMP Books Authors Peter Gulutzan, Trudy Pelzer Pub Date April 1999 ISBN 0879305681 Pages 1104 Price $55.96 This book contains complete descriptions of the new standards for syntax, data structures, and retrieval processes of SQL databases. As an example-based reference manual, it includes all of the CLI functions, information, schema tables, and status codes, as well as a working SQL database provided on the companion disk. _C, A reference manual_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0133262243&bfmtype=book) Publisher Prentice Hall Authors Samuel P. Harbison, Guy L. Steele Pub Date September 1994 ISBN 0133262243 Pages 480 Price $35.99 A new and improved revision of the bestselling C language reference. This manual introduces the notion of "Clean C", writing C code that can be compiled as a C++ program, C programming style that emphasizes correctness, portability, maintainability, and incorporates the ISO C Amendment 1 (1994) which specifies new facilities for writing portable, international programs in C. _C++ for Real Programmers_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0120499428&bfmtype=book) Publisher Academic Press, Incorporated Authors Jeff Alger, Jim Keogh Pub Date February 1998 ISBN 0120499428 Pages 388 Price $39.95 _C++ For Real Programmers_ bridges the gap between C++ as described in beginner and intermediate-level books and C++ as it is practiced by experts. Numerous valuable techniques are described, organized into three simple themes: indirection, class hierarchies, and memory management. It also provides in-depth coverage of template creation, exception handling, pointers and optimization techniques. The focus of the book is on ANSI C++ and, as such, is compiler independent. _C++ For Real Programmers_ is a revision of _Secrets of the C++ Masters_ and includes a new appendix comparing C++ with Java. The book comes with a 3.5" disk for Windows with source code. _Algorithms in C_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0201514257&bfmtype=book) Publisher Addison Wesley Longman, Inc. Authors Robert Sedgewick Pub Date April 1990 ISBN 0201514257 Pages 648 Price $45.75 _Algorithms in C_ describes a variety of algorithms in a number of areas of interest, including: sorting, searching, string-processing, and geometric, graph and mathematical algorithms. The book emphasizes fundamental techniques, providing readers with the tools to confidently implement, run, and debug useful algorithms. _Multithreaded Programming with Pthreads_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=0136807291&bfmtype=book) Publisher Prentice Hall Authors Bil Lewis, Daniel J. Berg Pub Date October 1997 ISBN 0136807291 Pages 432 Price $34.95 Based on the best-selling _Threads Primer_, _Multithreaded Programming with Pthreads_ gives you a solid understanding of Posix threads: what they are, how they work, when to use them, and how to optimize them. It retains the clarity and humor of _Threads Primer_, but includes expanded comparisons to Win32 and OS/2 implementations. Code examples tested on all of the major UNIX platforms are featured along with detailed explanations of how and why they use threads. _Programming the PERL DBI: Database Programming with PERL_ Available Barnes and Noble (http://service.bfast.com/bfast/click?bfmid=2181&sourceid=34233559&bfpid=1565926994&bfmtype=book) Publisher O'Reilly & Associates, Incorporated Authors Alligator Descartes, Tim Bunce Pub Date February 2000 ISBN 1565926994 Pages 400 Price $27.96 _Programming the Perl DBI_ is coauthored by Alligator Descartes, one of the most active members of the DBI community, and by Tim Bunce, the inventor of DBI. For the uninitiated, the book explains the architecture of DBI and shows you how to write DBI-based programs. For the experienced DBI dabbler, this book explains DBI's nuances and the peculiarities of each individual DBD. The book includes: * An introduction to DBI and its design. * How to construct queries and bind parameters. * Working with database, driver, and statement handles. * Debugging techniques. * Coverage of each existing DBD. * A complete reference to DBI. The Main Features of MySQL ========================== The following list describes some of the important characteristics of *MySQL*: * Fully multi-threaded using kernel threads. This means it can easily use multiple CPUs if available. * C, C++, Eiffel, Java, Perl, PHP, Python and Tcl APIs. *Note Clients::. * Works on many different platforms. *Note Which OS::. * Many column types: signed/unsigned integers 1, 2, 3, 4, and 8 bytes long, `FLOAT', `DOUBLE', `CHAR', `VARCHAR', `TEXT', `BLOB', `DATE', `TIME', `DATETIME', `TIMESTAMP', `YEAR', `SET', and `ENUM' types. *Note Column types::. * Very fast joins using an optimized one-sweep multi-join. * Full operator and function support in the `SELECT' and `WHERE' parts of queries. For example: mysql> SELECT CONCAT(first_name, " ", last_name) FROM tbl_name WHERE income/dependents > 10000 AND age > 30; * SQL functions are implemented through a highly optimized class library and should be as fast as possible! Usually there isn't any memory allocation at all after query initialization. * Full support for SQL `GROUP BY' and `ORDER BY' clauses. Support for group functions (`COUNT()', `COUNT(DISTINCT ...)', `AVG()', `STD()', `SUM()', `MAX()' and `MIN()'). * Support for `LEFT OUTER JOIN' and `RIGHT OUTER JOIN' with ANSI SQL and ODBC syntax. * You can mix tables from different databases in the same query (as of Version 3.22). * A privilege and password system that is very flexible and secure, and allows host-based verification. Passwords are secure because all password traffic is encrypted when you connect to a server. * ODBC (Open-DataBase-Connectivity) support for Win32 (with source). All ODBC 2.5 functions and many others. For example, you can use MS Access to connect to your *MySQL* server. *Note ODBC::. * Very fast B-tree disk tables with index compression. * Up to 32 indexes per table are allowed. Each index may consist of 1 to 16 columns or parts of columns. The maximum index length is 500 bytes (this may be changed when compiling *MySQL*). An index may use a prefix of a `CHAR' or `VARCHAR' field. * Fixed-length and variable-length records. * In-memory hash tables which are used as temporary tables. * Handles large databases. We are using *MySQL* with some databases that contain 50,000,000 records and we know of users that uses *MySQL* with 60,000 tables and about 5,000,000,000 rows * All columns have default values. You can use `INSERT' to insert a subset of a table's columns; those columns that are not explicitly given values are set to their default values. * Uses GNU Automake, Autoconf, and Libtool for portability. * Written in C and C++. Tested with a broad range of different compilers. * A very fast thread-based memory allocation system. * No memory leaks. *MySQL* has been tested with Purify, a commercial memory leakage detector. * Includes `myisamchk', a very fast utility for table checking, optimization, and repair. All of the functionality of `myisamchk' is also available through the SQL interface as well. *Note Maintenance::. * Full support for several different character sets, including ISO-8859-1 (Latin1), big5, ujis, and more. For example, the Scandinavian characters `a*', `a"' and `o"' are allowed in table and column names. * All data are saved in the chosen character set. All comparisons for normal string columns are case insensitive. * Sorting is done according to the chosen character set (the Swedish way by default). It is possible to change this when the *MySQL* server is started up. To see an example of very advanced sorting, look at the Czech sorting code. *MySQL* supports many different character sets that can be specified at compile and run time. * Aliases on tables and columns are allowed as in the SQL92 standard. * `DELETE', `INSERT', `REPLACE', and `UPDATE' return the number of rows that were changed (affected). It is possible to return the number of rows matched instead by setting a flag when connecting to the server. * Function names do not clash with table or column names. For example, `ABS' is a valid column name. The only restriction is that for a function call, no spaces are allowed between the function name and the `(' that follows it. *Note Reserved words::. * All *MySQL* programs can be invoked with the `--help' or `-?' options to obtain online assistance. * The server can provide error messages to clients in many languages. *Note Languages::. * Clients may connect to the *MySQL* server using TCP/IP Sockets, Unix Sockets (Unix), or Named Pipes (NT). * The *MySQL*-specific `SHOW' command can be used to retrieve information about databases, tables, and indexes. The `EXPLAIN' command can be used to determine how the optimizer resolves a query. How Stable Is MySQL? ==================== This section addresses the questions "How stable is *MySQL*?" and "Can I depend on *MySQL* in this project?" We will try to clarify some issues and to answer some of the more important questions that seem to concern many people. This section has been put together from information gathered from the mailing list (which is very active in reporting bugs). At TcX, *MySQL* has worked without any problems in our projects since mid-1996. When *MySQL* was released to a wider public, we noticed that there were some pieces of "untested code" that were quickly found by the new users who made queries in a manner different than our own. Each new release has had fewer portability problems than the previous one (even though each has had many new features). Each release of *MySQL* has been usable, and there have been problems only when users start to use code from the "gray zones." Naturally, outside users don't know what the gray zones are; this section attempts to indicate those that are currently known. The descriptions deal with Version 3.23 of *MySQL*. All known and reported bugs are fixed in the latest version, with the exception of the bugs listed in the bugs section, which are things that are design-related. *Note Bugs::. *MySQL* is written in multiple layers and different independent modules. These modules are listed below with an indication of how well-tested each of them is: *The ISAM table handler -- Stable* This manages storage and retrieval of all data in *MySQL* Version 3.22 and earlier. In all *MySQL* releases there hasn't been a single (reported) bug in this code. The only known way to get a corrupted table is to kill the server in the middle of an update. Even that is unlikely to destroy any data beyond rescue, because all data are flushed to disk between each query. There hasn't been a single bug report about lost data because of bugs in *MySQL*. *The MyISAM table handler -- Stable* This is new in *MySQL* Version 3.23. It's largely based on the ISAM table code but has a lot of new and very useful features. *The parser and lexical analyser -- Stable* There hasn't been a single reported bug in this system for a long time. *The C client code -- Stable* No known problems. In early Version 3.20 releases, there were some limitations in the send/receive buffer size. As of Version 3.21, the buffer size is now dynamic up to a default of 16M. *Standard client programs -- Stable* These include `mysql', `mysqladmin', `mysqlshow', `mysqldump', and `mysqlimport'. *Basic SQL -- Stable* The basic SQL function system and string classes and dynamic memory handling. Not a single reported bug in this system. *Query optimizer -- Stable* *Range optimizer -- Stable* *Join optimizer -- Stable* *Locking -- Gamma* This is very system-dependent. On some systems there are big problems using standard OS locking (`fcntl()'). In these cases, you should run the *MySQL* daemon with the `--skip-locking' flag. Problems are known to occur on some Linux systems, and on SunOS when using NFS-mounted file systems. *Linux threads -- Stable* The major problem found has been with the `fcntl()' call, which is fixed by using the `--skip-locking' option to `mysqld'. Some people have reported lockup problems with Version 0.5. LinuxThreads will need to be recompiled if you plan to use 1000+ concurrent connections. Although it is possible to run that many connections with the default LinuxThreads (however, you will never go above 1021), the default stack spacing of 2 MB makes the application unstable, and we have been able to reproduce a coredump after creating 1021 idle connections. *Note Linux::. *Solaris 2.5+ pthreads -- Stable* We use this for all our production work. *MIT-pthreads (Other systems) -- Stable* There have been no reported bugs since Version 3.20.15 and no known bugs since Version 3.20.16. On some systems, there is a "misfeature" where some operations are quite slow (a 1/20 second sleep is done between each query). Of course, MIT-pthreads may slow down everything a bit, but index-based `SELECT' statements are usually done in one time frame so there shouldn't be a mutex locking/thread juggling. *Other thread implementions -- Beta - Gamma* The ports to other systems are still very new and may have bugs, possibly in *MySQL*, but most often in the thread implementation itself. *`LOAD DATA ...', `INSERT ... SELECT' -- Stable* Some people thought they had found bugs here, but these usually have turned out to be misunderstandings. Please check the manual before reporting problems! *`ALTER TABLE' -- Stable* Small changes in Version 3.22.12. *DBD -- Stable* Now maintained by Jochen Wiedmann (). Thanks! *`mysqlaccess' -- Stable* Written and maintained by Yves Carlier (). Thanks! *`GRANT' -- Stable* Big changes made in *MySQL* Version 3.22.12. **MyODBC* (uses ODBC SDK 2.5) -- Gamma* It seems to work well with some programs. *Replication - Beta / Gamma* We are still working on replication, so don't expect this to be rock solid yet. On the other hand, some *MySQL* users are already using this with good results. *BDB Tables - Beta* The Berkeley DB code is very stable, but we are still improving the interface between *MySQL* and BDB tables, so it will take some time before this is as tested as the other table types. *InnoDB Tables - Alpha* This is a very recent addition to `MySQL' and is not very tested yet. *Automatic recovery of MyISAM tables - Beta* This only affects the new code that checks if the table was closed properly on open and executes an automatic check/repair of the table if it wasn't. *MERGE tables - Beta / Gamma* The usage of keys on `MERGE' tables is still not that tested. The other part of the `MERGE' code is quite well tested. *FULLTEXT - Beta* Text search seems to work, but is still not widely used. *MySQL AB* provides e-mail support for paying customers, but the *MySQL* mailing list usually provides answers to common questions. Bugs are usually fixed right away with a patch; for serious bugs, there is almost always a new release. Year 2000 Compliance ==================== *MySQL* itself has no problems with Year 2000 (Y2K) compliance: * *MySQL* uses Unix time functions and has no problems with dates until `2069'; all 2-digit years are regarded to be in the range `1970' to `2069', which means that if you store `01' in a `year' column, *MySQL* treats it as `2001'. * All *MySQL* date functions are stored in one file `sql/time.cc' and coded very carefully to be year 2000-safe. * In *MySQL* Version 3.22 and later, the new `YEAR' column type can store years `0' and `1901' to `2155' in 1 byte and display them using 2 or 4 digits. You may run into problems with applications that use *MySQL* in a way that is not Y2K-safe. For example, many old applications store or manipulate years using 2-digit values (which are ambiguous) rather than 4-digit values. This problem may be compounded by applications that use values such as `00' or `99' as "missing" value indicators. Unfortunately, these problems may be difficult to fix, because different applications may be written by different programmers, each of whom may use a different set of conventions and date-handling functions. Here is a simple demonstration illustrating that *MySQL* doesn't have any problems with dates until the year 2030: mysql> DROP TABLE IF EXISTS y2k; Query OK, 0 rows affected (0.01 sec) mysql> CREATE TABLE y2k (date date, date_time datetime, time_stamp timestamp); Query OK, 0 rows affected (0.00 sec) mysql> INSERT INTO y2k VALUES -> ("1998-12-31","1998-12-31 23:59:59",19981231235959), -> ("1999-01-01","1999-01-01 00:00:00",19990101000000), -> ("1999-09-09","1999-09-09 23:59:59",19990909235959), -> ("2000-01-01","2000-01-01 00:00:00",20000101000000), -> ("2000-02-28","2000-02-28 00:00:00",20000228000000), -> ("2000-02-29","2000-02-29 00:00:00",20000229000000), -> ("2000-03-01","2000-03-01 00:00:00",20000301000000), -> ("2000-12-31","2000-12-31 23:59:59",20001231235959), -> ("2001-01-01","2001-01-01 00:00:00",20010101000000), -> ("2004-12-31","2004-12-31 23:59:59",20041231235959), -> ("2005-01-01","2005-01-01 00:00:00",20050101000000), -> ("2030-01-01","2030-01-01 00:00:00",20300101000000), -> ("2050-01-01","2050-01-01 00:00:00",20500101000000); Query OK, 13 rows affected (0.01 sec) Records: 13 Duplicates: 0 Warnings: 0 mysql> SELECT * FROM y2k; +------------+---------------------+----------------+ | date | date_time | time_stamp | +------------+---------------------+----------------+ | 1998-12-31 | 1998-12-31 23:59:59 | 19981231235959 | | 1999-01-01 | 1999-01-01 00:00:00 | 19990101000000 | | 1999-09-09 | 1999-09-09 23:59:59 | 19990909235959 | | 2000-01-01 | 2000-01-01 00:00:00 | 20000101000000 | | 2000-02-28 | 2000-02-28 00:00:00 | 20000228000000 | | 2000-02-29 | 2000-02-29 00:00:00 | 20000229000000 | | 2000-03-01 | 2000-03-01 00:00:00 | 20000301000000 | | 2000-12-31 | 2000-12-31 23:59:59 | 20001231235959 | | 2001-01-01 | 2001-01-01 00:00:00 | 20010101000000 | | 2004-12-31 | 2004-12-31 23:59:59 | 20041231235959 | | 2005-01-01 | 2005-01-01 00:00:00 | 20050101000000 | | 2030-01-01 | 2030-01-01 00:00:00 | 20300101000000 | | 2050-01-01 | 2050-01-01 00:00:00 | 00000000000000 | +------------+---------------------+----------------+ 13 rows in set (0.00 sec) This shows that the `DATE' and `DATETIME' types will not give any problems with future dates (they handle dates until the year 9999). The `TIMESTAMP' type, which is used to store the current time, has a range up to only `2030-01-01'. `TIMESTAMP' has a range of `1970' to `2030' on 32-bit machines (signed value). On 64-bit machines it handles times up to `2106' (unsigned value). Even though *MySQL* is Y2K-compliant, it is your responsibility to provide unambiguous input. See *Note Y2K issues:: for *MySQL*'s rules for dealing with ambiguous date input data (data containing 2-digit year values). General SQL Information and Tutorials ===================================== The following book has been recommended by several people on the *MySQL* mailing list: Judith S. Bowman, Sandra L. Emerson and Marcy Darnovsky _The Practical SQL Handbook: Using Structured Query Language_ Second Edition Addison-Wesley ISBN 0-201-62623-3 http://www.awl.com The following book has also received some recommendations by *MySQL* users: Martin Gruber _Understanding SQL_ ISBN 0-89588-644-8 Publisher Sybex 510 523 8233 Alameda, CA USA A SQL tutorial is available on the net at http://w3.one.net/~jhoffman/sqltut.htm Useful MySQL-related Links ========================== Apart from the following links, you can find and download a lot of *MySQL* programs, tools and APIs from the Contrib directory (http://www.mysql.com/Downloads/Contrib/). *MySQL* Tutorials and Manuals --------------------- MySQL Myths Debunked (http://netgraft.com/~mbac/research/mysqlmyths.html) *MySQL* used in the real world. `http://www.4t2.com/mysql' Information about the German MySQL mailing list. `http://www2.rent-a-database.de/mysql/' *MySQL* handbook in German. `http://www.bitmover.com:8888//home/bk/mysql' Web access to the *MySQL* BitKeeper repository. `http://www.analysisandsolutions.com/code/mybasic.htm' Beginners *MySQL* Tutorial on how to install and set up *MySQL* on a Windows machine. `http://www.devshed.com/Server_Side/MySQL/' A lot of *MySQL* tutorials. `http://mysql.hitstar.com/' MySQL manual in Chinese. `http://www.linuxplanet.com/linuxplanet/tutorials/1046/1/' Setting Up a *MySQL*-based Web site. `http://www.hotwired.com/webmonkey/backend/tutorials/tutorial1.html' *MySQL*-Perl tutorial. `http://www.iserver.com/support/contrib/perl5/modules.html' Installing new Perl modules that require locally installed modules. `http://www.hotwired.com/webmonkey/databases/tutorials/tutorial4.html' PHP/*MySQL* Tutorial. `http://www.useractive.com/' Hands on tutorial for *MySQL*. Porting MySQL/Using MySQL on Different Systems ---------------------------------------------- `http://xclave.macnn.com/MySQL/' The Mac OS Xclave. Running *MySQL* on Mac OS X. `http://www.prnet.de/RegEx/mysql.html' MySQL for Mac OS X Server. `http://www.latencyzero.com/macosx/mysql.html' Building MySQL for Mac OS X. `http://www.essencesw.com/Software/mysqllib.html' New Client libraries for the Mac OS Classic (Macintosh). `http://www.lilback.com/macsql/' Client libraries for Mac OS Classic (Macintosh). `http://sixk.maniasys.com/index_en.html' MySQL for Amiga Perl-related Links ------------------ `http://dbimysql.photoflux.com/' Perl DBI with *MySQL* FAQ. MySQL Discussion Forums ----------------------- `http://www.weberdev.com/' Examples using *MySQL*; (check Top 20) `http://futurerealm.com/forum/futureforum.htm' FutureForum Web Discussion Software. Commercial Applications that Support MySQL ------------------------------------------ `http://www.supportwizard.com/' SupportWizard; Interactive helpdesk on the Web (This product includes a licensed copy of *MySQL*.) `http://www.sonork.com/' Sonork, Instant Messenger that is not only Internet oriented. It's focused on private networks and on small to medium companies. Client is free, server is free for up to 5 seats. `http://www.stweb.org/' StWeb - Stratos Web and Application server - An easy-to-use, cross platform, Internet/Intranet development and deployment system for development of web-enabled applications. The standard version of StWeb has a native interface to *MySQL* database. `http://www.rightnowtech.com/' Right Now Web; Web automation for customer service. `http://www.icaap.org/Bazaar/' Bazaar; Interactive Discussion Forums with Web interface. `http://www.phonesweep.com/' PhoneSweepT is the world's first commercial Telephone Scanner. Many break-ins in recent years have come not through the Internet, but through unauthorized dial-up modems. PhoneSweep lets you find these modems by repeatedly placing phone calls to every phone number that your organization controls. PhoneSweep has a built-in expert system that can recognize more than 250 different kinds of remote-access programs, including Carbon Copy(TM), pcANYWHERE(TM), and Windows NT RAS. All information is stored in the SQL database. It then generates a comprehensive report detailing which services were discovered on which dial-up numbers in your organization. SQL Clients and Report Writers ------------------------------ urSQL (http://www.urbanresearch.com/software/utils/urbsql/index.html) SQL Editor and Query Utility. Custom syntax highlighting, editable results grid, exportable result-sets, basic *MySQL* admin functions, Etc.. For Windows. MySQL Data Manager (http://www.edatanew.com/) *MySQL* Data Manager * is platform independent web client (written in perl) for *MySQL* server over TCP/IP. `http://ksql.sourceforge.net/' KDE *MySQL* client. `http://www.ecker-software.de' A Windows GUI client by David Ecker. `http://www.icaap.org/software/kiosk/' Kiosk; a *MySQL* client for database management. Written in Perl. Will be a part of Bazaar. `http://www.casestudio.com/' Db design tool that supports MySQL 3.23. `http://home.skif.net/~voland/zeos/eng/index.html' Zeos - A client that supports *MySQL*, Interbase and PostgreSQL. `http://www.geocities.com/SiliconValley/Ridge/4280/GenericReportWriter/grwhome.html' A free report writer in Java `http://www.javaframework.de' MySQLExport - Export of *MySQL* create statements and data in a lot of different formats (SQL, HTML, CVS, text, ZIP, GZIP...) `http://dlabs.4t2.com' M2D, a *MySQL* Administration client for Windows. M2D supports administration of *MySQL* databases, creation of new databases and tables, editing, and more. `http://www.scibit.com/Products/Software/Utils/Mascon.asp' Mascon is a powerful Win32 GUI for administering MySQL databases. `http://www.rtlabs.com/' MacSQL Monitor. GUI for MySQL, ODBC, and JDBC databases for the Mac OS. Distributions that Include MySQL -------------------------------- `http://www.suse.com/' SuSE Linux (6.1 and above) `http://www.redhat.com/' RedHat Linux (7.0 and above) `http://distro.conectiva.com.br' Conectiva Linux (4.0 and above) Web Development Tools that Support *MySQL* ------------------------------------------ `http://www.php.net/' PHP: A server-side HTML-embedded scripting language. `http://www.midgard-project.org' The Midgard Application Server; a powerful Web development environment based on *MySQL* and PHP. `http://www.smartworker.org' SmartWorker is a platform for Web application development. `http://xsp.lentus.se/' XSP: e(X)tendible (S)erver (P)ages and is a HTML embedded tag language written in Java (previously known as XTAGS.) `http://www.dbServ.de/' dbServ is an extension to a web server to integrate database output into your HTML code. You may use any HTML function in your output. Only the client will stop you. It works as standalone server or as Java servlet. `http://www.chilisoft.com/' Platform independent ASP from Chili!Soft `http://www.voicenet.com/~zellert/tjFM' A JDBC driver for *MySQL*. `http://www.wernhart.priv.at/php/' *MySQL* + PHP demos. `http://www.dbwww.com/' ForwardSQL: HTML interface to manipulate *MySQL* databases. `http://www.daa.com.au/~james/www-sql/' WWW-SQL: Display database information. `http://www.minivend.com/minivend/' Minivend: A Web shopping cart. `http://www.heitml.com/' HeiTML: A server-side extension of HTML and a 4GL language at the same time. `http://www.metahtml.com/' Metahtml: A Dynamic Programming Language for WWW Applications. `http://www.binevolve.com/' VelocityGen for Perl and Tcl. `http://hawkeye.net/' Hawkeye Internet Server Suite. `http://www.fastflow.com/' Network Database Connection For Linux `http://www.wdbi.net/' WDBI: Web browser as a universal front end to databases which supports *MySQL* well. `http://www.webgroove.com/' WebGroove Script: HTML compiler and server-side scripting language. `http://www.ihtml.com/' A server-side Web site scripting language. `ftp://ftp.igc.apc.org/pub/myodbc/README' How to use *MySQL* with ColdFusion on Solaris. `http://calistra.com/MySQL/' Calistra's ODBC *MySQL* Administrator. `http://www.webmerger.com' Webmerger - This CGI tool interprets files and generates dynamic output based on a set of simple tags. Ready-to-run drivers for *MySQL* and PostgreSQL through ODBC. `http://phpclub.net/' PHPclub - Tips and tricks for PHP. `http://www.penguinservices.com/scripts' *MySQL* and Perl Scripts. `http://www.widgetchuck.com' The Widgetchuck; Web Site Tools and Gadgets `http://www.adcycle.com/' AdCycle - advertising management software. `http://sourceforge.net/projects/pwpage/' pwPage - provides an extremely fast and simple approach to the creation of database forms. That is, if a database table exists and an HTML page has been constructed using a few simple guidelines, pwPage can be immediately used for table data selections, insertions, updates, deletions and selectable table content reviewing. `http://www.omnis-software.com/products/studio/studio.html' OMNIS Studio is a rapid application development (RAD) tool. `http://www.webplus.com' talentsoft Web+ 4.6 - a powerful and comprehensive development language for use in creating web-based client/server applications without writing complicated, low-level, and time-consuming CGI programs. Database Design Tools with MySQL Support ---------------------------------------- `http://www.mysql.com/documentation/dezign/' "DeZign for databases" is a database development tool that uses an entity relationship diagram (ERD). Web Servers with *MySQL* Tools ------------------------------ `http://bourbon.netvision.net.il/mysql/mod_auth_mysql/' An Apache authentication module. `http://www.roxen.com/' The Roxen Challenger Web server. Extensions for Other Programs ----------------------------- `http://www.seawood.org/msql_bind/' *MySQL* support for BIND (The Internet Domain Name Server). `http://www.inet-interactive.com/sendmail/' *MySQL* support for Sendmail and Procmail. Using *MySQL* with Other Programs --------------------------------- `http://www.iserver.com/support/addonhelp/database/mysql/msaccess.html' Using *MySQL* with Access. `http://www.iserver.com/support/contrib/perl5/modules.html' Installing new Perl modules that require locally installed modules. ODBC-related Links ------------------ `http://www.iodbc.org/' Popular iODBC Driver Manager (libiodbc) now available as Open Source. `http://users.ids.net/~bjepson/freeODBC/' The FreeODBC Pages. `http://genix.net/unixODBC/' The unixODBC Project goals are to develop and promote unixODBC to be the definitive standard for ODBC on the Linux platform. This is to include GUI support for KDE. `http://www.sw-soft.com/products/BtrieveODBC/' A *MySQL*-based ODBC driver for Btrieve. *API*-related Links ------------------- `http://www.jppp.com/' Partially implemented TDataset-compatible components for *MySQL*. `http://www.riverstyx.net/qpopmysql/' qpopmysql - A patch to allow POP3 authentication from a *MySQL* database. There's also a link to Paul Khavkine's patch for Procmail to allow any MTA to deliver to users in a *MySQL* database. `http://www.pbc.ottawa.on.ca' Visual Basic class generator for Active X. `http://www.essencesw.com/Software/mysqllib.html' New Client libraries for the Mac OS Classic (Macintosh). `http://www.lilback.com/macsql/' Client libraries for the Macintosh. `http://www.essencesw.com/Plugins/mysqlplug.html' Plugin for REALbasic (for Macintosh) `http://www.iis.ee.ethz.ch/~neeri/macintosh/gusi-qa.html' A library that emulates BSD sockets and pthreads on Macintosh. This can be used if you want to compile the *MySQL* client library on Mac. It could probably even be sued to port *MySQL* to Macintosh, but we don't know of anyone that has tried that. `http://www.dedecker.net/jessie/scmdb/' SCMDB - an add-on for SCM that ports the *MySQL* C library to scheme (SCM). With this library scheme developers can make connections to a *MySQL* database and use embedded SQL in their programs. Other *MySQL*-related Links --------------------------- SAT (http://www.satisoft.com/) The Small Application Toolkit (SAT) is a collection of utilities intended to simplify the development of small, multi-user, GUI based applications in a (Microsoft -or- X) Windows Client / Unix Server environment. `http://www.wix.com/mysql-hosting/' Registry of Web providers who support *MySQL*. `http://www.softagency.co.jp/mysql/index.en.html' Links about using *MySQL* in Japan/Asia. `http://abattoir.cc.ndsu.nodak.edu/~nem/mysql/udf/' *MySQL* UDF Registry. `http://www.open.com.au/products.html' Commercial Web defect tracking system. `http://www.stonekeep.com/pts/' PTS: Project Tracking System. `http://tomato.nvgc.vt.edu/~hroberts/mot' Job and software tracking system. `http://www.cynergi.net/exportsql/' ExportSQL: A script to export data from Access95+. `http://SAL.KachinaTech.COM/H/1/MYSQL.html' SAL (Scientific Applications on Linux) *MySQL* entry. `http://www.infotech-nj.com/itech/index.shtml' A consulting company which mentions *MySQL* in the right company. `http://www.pmpcs.com/' PMP Computer Solutions. Database developers using *MySQL* and `mSQL'. `http://www.aewa.org/' Airborne Early Warning Association. `http://www.dedserius.com/y2kmatrix/' Y2K tester. SQL and Database Interfaces --------------------------- `http://java.sun.com/products/jdbc/' The JDBC database access API. `http://www.gagme.com/mysql' Patch for `mSQL' Tcl. `http://www.amsoft.ru/easysql/' EasySQL: An ODBC-like driver manager. `http://www.lightlink.com/hessling/rexxsql.html' A REXX interface to SQL databases. `http://www.mytcl.cx/' Tcl interface based on tcl-sql with many bugfixes. `http://www.binevolve.com/~tdarugar/tcl-sql/' Tcl interface. `http://www.contrib.andrew.cmu.edu/~shadow/sql.html' SQL Reference Page with a lot of interesting links. Examples of MySQL Use --------------------- `http://www.little6.com/about/linux/' Little6 Inc., An online contract and job finding site that is powered by *MySQL*, PHP3, and Linux. `http://www.delec.com/is/products/prep/examples/BookShelf/index.html' DELECis - A tool that makes it very easy to create an automatically generated table documentation. They have used *MySQL* as an example. `http://www.worldrecords.com' World Records - A search engine for information about music that uses *MySQL* and PHP. `http://www.webtechniques.com/archives/1998/01/note/' A Contact Database using *MySQL* and PHP. `http://modems.rosenet.net/mysql/' Web based interface and Community Calendar with PHP. `http://www.odbsoft.com/cook/sources.htm' Perl package to generate html from a SQL table structure and for generating SQL statements from an html form. `http://www.gusnet.cx/proj/telsql/' Basic telephone database using `DBI'/`DBD'. `http://tecfa.unige.ch/guides/java/staf2x/ex/jdbc/coffee-break' JDBC examples by Daniel K. Schneider. `http://www.spade.com/linux/howto/PostgreSQL-HOWTO-41.html' SQL BNF `http://www.ooc.com/' Object Oriented Concepts Inc; CORBA applications with examples in source. `http://www.pbc.ottawa.on.ca/' DBWiz; Includes an example of how to manage cursors in VB. `http://keilor.cs.umass.edu/pluribus/' Pluribus is a free search engine that learns to improve the quality of its results over time. Pluribus works by recording which pages a user prefers among those returned for a query. A user votes for a page by selecting it; Pluribus then uses that knowledge to improve the quality of the results when someone else submits the same (or similar) query. Uses PHP and *MySQL*. `http://www.stopbit.com/' Stopbit - A technology news site using *MySQL* and PHP. `http://www.linuxsupportline.com/~kalendar/' KDE based calendar manager - The calendar manager has both single user (file based) and multi-user (*MySQL* database) support. `http://tim.desert.net/~tim/imger/' Example of storing/retrieving images with *MySQL* and CGI. `http://www.penguinservices.com/scripts' Online shopping cart system. `http://www.city-gallery.com/album/' Old Photo Album - The album is a collaborative popular history of photography project that generates all pages from data stored in a *MySQL* database. Pages are dynamically generated through a php3 interface to the database content. Users contribute images and descriptions. Contributed images are stored on the web server to avoid storing them in the database as BLOBs. All other information is stored on the shared *MySQL* server. General Database Links ---------------------- `http://www.pcslink.com/~ej/dbweb.html' Database Jump Site `http://black.hole-in-the.net/guy/webdb/' Homepage of the webdb-l (Web Databases) mailing list. `http://www.symbolstone.org/technology/perl/DBI/index.html' Perl `DBI'/`DBD' modules homepage. `http://www.student.uni-koeln.de/cygwin/' Cygwin tools. Unix on top of Windows. `http://dbasecentral.com/' dbasecentral.com; Development and distribution of powerful and easy-to-use database applications and systems. `http://www.tek-tips.com/' Tek-Tips Forums are 800+ independent peer-to-peer non-commercial support forums for Computer Professionals. Features include automatic e-mail notification of responses, a links library, and member confidentiality guaranteed. `http://www.public.asu.edu/~peterjn/btree/' B-Trees: Balanced Tree Data Structures. `http://www.fit.qut.edu.au/~maire/baobab/lecture/sld001.htm' A lecture about B-Trees. There are also many Web pages that use *MySQL*. *Note Users::. Send any additions to this list to . We now require that you show a *MySQL* logo somewhere if you wish your site to be added. It is okay to have it on a "used tools" page or something similar. MySQL Mailing Lists ******************* This chapter introduces you to the *MySQL* mailing lists, and gives some guidelines as to how to use them. The MySQL Mailing Lists ======================= To subscribe to the main *MySQL* mailing list, send a message to the electronic mail address . To unsubscribe from the main *MySQL* mailing list, send a message to the electronic mail address . Only the address to which you send your messages is significant. The subject line and the body of the message are ignored. If your reply address is not valid, you can specify your address explicitly. Adding a hyphen to the subscribe or unsubscribe command word, followed by your address with the `@' character in your address replaced by a `='. For example, to subscribe `your_name@host.domain', send a message to `mysql-subscribe-your_name=host.domain@lists.mysql.com'. Mail to or is handled automatically by the ezmlm mailing list processor. Information about ezmlm is available at The ezmlm Website (http://www.ezmlm.org). To post a message to the list itself, send your message to `mysql@lists.mysql.com'. However, please _do not_ send mail about subscribing or unsubscribing to , because any mail sent to that address is distributed automatically to thousands of other users. Your local site may have many subscribers to . If so, it may have a local mailing list, so that messages sent from `lists.mysql.com' to your site are propagated to the local list. In such cases, please contact your system administrator to be added to or dropped from the local *MySQL* list. The following *MySQL* mailing lists exist: ` announce' This is for announcement of new versions of *MySQL* and related programs. This is a low volume list all *MySQL* users should subscribe to. ` mysql' The main list for general *MySQL* discussion. Please note that some topics are better discussed on the more-specialized lists. If you post to the wrong list, you may not get an answer! ` mysql-digest' The `mysql' list in digest form. That means you get all individual messages, sent as one large mail message once a day. ` bugs' On this list you should only post a full, repeatable bug report using the `mysqlbug' script (if you are running on Windows, you should include a description of the operating system and the *MySQL* version). Preferably, you should test the problem using the latest stable or development version of *MySQL* before posting! Anyone should be able to repeat the bug by just using `mysql test < script' on the included test case. All bugs posted on this list will be corrected or documented in the next *MySQL* release! If there are only small code changes involved, we will also post a patch that fixes the problem. ` bugs-digest' The `bugs' list in digest form. ` internals' A list for people who work on the *MySQL* code. On this list one can also discuss *MySQL* development and post patches. ` internals-digest' A digest version of the `internals' list. ` java' Discussion about *MySQL* and Java. Mostly about the JDBC drivers. ` java-digest' A digest version of the `java' list. ` win32' All things concerning *MySQL* on Microsoft operating systems such as Win95, Win98, NT, and Win2000. ` win32-digest' A digest version of the `win32' list. ` myodbc' All things about connecting to *MySQL* with ODBC. ` myodbc-digest' A digest version of the `myodbc' list. ` plusplus' All things concerning programming with the C++ API to *MySQL*. ` plusplus-digest' A digest version of the `plusplus' list. ` msql-mysql-modules' A list about the Perl support in *MySQL*. msql-mysql-modules ` msql-mysql-modules-digest' A digest version of the `msql-mysql-modules' list. You subscribe or unsubscribe to all lists in the same way as described above. In your subscribe or unsubscribe message, just put the appropriate mailing list name rather than `mysql'. For example, to subscribe to or unsubscribe from the `myodbc' list, send a message to or . The following table shows some *MySQL* mailing in other languages than English. Note that these are not operated by *MySQL AB*, so we can't guarantee the quality on these. ` A French mailing list' ` A Korean mailing list' Email `subscribe mysql your@email.address' to this list. ` A German mailing list' Email `subscribe mysql-de your@email.address' to this list. You can find information about this mailing list at `http://www.4t2.com/mysql'. ` A Portugese mailing list' Email `subscribe mysql-br your@email.address' to this list. ` A Spanish mailing list' Email `subscribe mysql your@email.address' to this list. Asking Questions or Reporting Bugs ================================== Before posting a bug report or question, please do the following: * Start by searching the *MySQL* online manual at: `http://www.mysql.com/documentation/manual.php' We try to keep the manual up to date by updating it frequently with solutions to newly found problems! * Search the *MySQL* mailing list archives: `http://www.mysql.com/documentation/' * You can also use `http://www.mysql.com/search.html' to search all the Web pages (including the manual) that are located at `http://www.mysql.com/'. If you can't find an answer in the manual or the archives, check with your local *MySQL* expert. If you still can't find an answer to your question, go ahead and read the next section about how to send mail to . How to Report Bugs or Problems ============================== Writing a good bug report takes patience, but doing it right the first time saves time for us and for you. A good bug report containing a full test case for the bug will make it very likely that we will fix it in the next release. This section will help you write your report correctly so that you don't waste your time doing things that may not help us much or at all. We encourage everyone to use the `mysqlbug' script to generate a bug report (or a report about any problem), if possible. `mysqlbug' can be found in the `scripts' directory in the source distribution, or, for a binary distribution, in the `bin' directory under your *MySQL* installation directory. If you are unable to use `mysqlbug', you should still include all the necessary information listed in this section. The `mysqlbug' script helps you generate a report by determining much of the following information automatically, but if something important is missing, please include it with your message! Please read this section carefully and make sure that all the information described here is included in your report. The normal place to report bugs and problems is . If you can make a test case that clearly demonstrates the bug, you should post it to the list. Note that on this list you should only post a full, repeatable bug report using the `mysqlbug' script. If you are running on Windows, you should include a description of the operating system and the *MySQL* version. Preferably, you should test the problem using the latest stable or development version of *MySQL* before posting! Anyone should be able to repeat the bug by just using "`mysql test < script'" on the included test case or run the shell or perl script that is included in the bug report. All bugs posted on the `bugs' list will be corrected or documented in the next *MySQL* release! If there are only small code changes involved to correct this problem, we will also post a patch that fixes the problem. Remember that it is possible to respond to a message containing too much information, but not to one containing too little. Often people omit facts because they think they know the cause of a problem and assume that some details don't matter. A good principle is: if you are in doubt about stating something, state it! It is a thousand times faster and less troublesome to write a couple of lines more in your report than to be forced to ask again and wait for the answer because you didn't include enough information the first time. The most common errors are that people don't indicate the version number of the *MySQL* distribution they are using, or don't indicate what platform they have *MySQL* installed on (including the platform version number). This is highly relevant information, and in 99 cases out of 100 the bug report is useless without it! Very often we get questions like, "Why doesn't this work for me?" then we find that the feature requested wasn't implemented in that *MySQL* version, or that a bug described in a report has been fixed already in newer *MySQL* versions. Sometimes the error is platform dependent; in such cases, it is next to impossible to fix anything without knowing the operating system and the version number of the platform. Remember also to provide information about your compiler, if it is related to the problem. Often people find bugs in compilers and think the problem is *MySQL*-related. Most compilers are under development all the time and become better version by version. To determine whether or not your problem depends on your compiler, we need to know what compiler is used. Note that every compiling problem should be regarded as a bug report and reported accordingly. It is most helpful when a good description of the problem is included in the bug report. That is, a good example of all the things you did that led to the problem and the problem itself exactly described. The best reports are those that include a full example showing how to reproduce the bug or problem. *Note Reproduceable test case::. If a program produces an error message, it is very important to include the message in your report! If we try to search for something from the archives using programs, it is better that the error message reported exactly matches the one that the program produces. (Even the case should be observed!) You should never try to remember what the error message was; instead, copy and paste the entire message into your report! If you have a problem with MyODBC, you should try to generate a MyODBC trace file. *Note MyODBC bug report::. Please remember that many of the people who will read your report will do so using an 80-column display. When generating reports or examples using the `mysql' command line tool, you should therefore use the `--vertical' option (or the `\G' statement terminator) for output that would exceed the available width for such a display (for example, with the `EXPLAIN SELECT' statement; see the example below). Please include the following information in your report: * The version number of the *MySQL* distribution you are using (for example, *MySQL* Version 3.22.22). You can find out which version you are running by executing `mysqladmin version'. `mysqladmin' can be found in the `bin' directory under your *MySQL* installation directory. * The manufacturer and model of the machine you are working on. * The operating system name and version. For most operating systems, you can get this information by executing the Unix command `uname -a'. * Sometimes the amount of memory (real and virtual) is relevant. If in doubt, include these values. * If you are using a source distribution of *MySQL*, the name and version number of the compiler used is needed. If you have a binary distribution, the distribution name is needed. * If the problem occurs during compilation, include the exact error message(s) and also a few lines of context around the offending code in the file where the error occurred. * If `mysqld' died, you should also report the query that crashed `mysqld'. You can usually find this out by running `mysqld' with logging enabled. *Note Using log files::. * If any database table is related to the problem, include the output from `mysqldump --no-data db_name tbl_name1 tbl_name2 ...'. This is very easy to do and is a powerful way to get information about any table in a database that will help us create a situation matching the one you have. * For speed-related bugs or problems with `SELECT' statements, you should always include the output of `EXPLAIN SELECT ...', and at least the number of rows that the `SELECT' statement produces. The more information you give about your situation, the more likely it is that someone can help you! For example, the following is an example of a very good bug report (it should of course be posted with the `mysqlbug' script): Example run using the `mysql' command line tool (note the use of the `\G' statement terminator for statements whose output width would otherwise exceed that of an 80-column display device): mysql> SHOW VARIABLES; mysql> SHOW COLUMNS FROM ...\G mysql> EXPLAIN SELECT ...\G mysql> FLUSH STATUS; mysql> SELECT ...; mysql> SHOW STATUS; * If a bug or problem occurs while running *mysqld*, try to provide an input script that will reproduce the anomaly. This script should include any necessary source files. The more closely the script can reproduce your situation, the better. If you can make a repeatable test case, you should post this to for a high priority treatment! If you can't provide a script, you should at least include the output from `mysqladmin variables extended-status processlist' in your mail to provide some information of how your system is performing! * If you can't produce a test case in a few rows, or if the test table is too big to be mailed to the mailing list (more than 10 rows), you should dump your tables using `mysqldump' and create a `README' file that describes your problem. Create a compressed archive of your files using `tar' and `gzip' or `zip', and use `ftp' to transfer the archive to `ftp://support.mysql.com/pub/mysql/secret/'. Then send a short description of the problem to . * If you think that *MySQL* produces a strange result from a query, include not only the result, but also your opinion of what the result should be, and an account describing the basis for your opinion. * When giving an example of the problem, it's better to use the variable names, table names, etc., that exist in your actual situation than to come up with new names. The problem could be related to the name of a variable or table! These cases are rare, perhaps, but it is better to be safe than sorry. After all, it should be easier for you to provide an example that uses your actual situation, and it is by all means better for us. In case you have data you don't want to show to others, you can use `ftp' to transfer it to `ftp://support.mysql.com/pub/mysql/secret/'. If the data are really top secret and you don't want to show them even to us, then go ahead and provide an example using other names, but please regard this as the last choice. * Include all the options given to the relevant programs, if possible. For example, indicate the options that you use when you start the `mysqld' daemon and that you use to run any *MySQL* client programs. The options to programs like `mysqld' and `mysql', and to the `configure' script, are often keys to answers and are very relevant! It is never a bad idea to include them anyway! If you use any modules, such as Perl or PHP, please include the version number(s) of those as well. * If your question is related to the privilege system, please include the output of `mysqlaccess', the output of `mysqladmin reload', and all the error messages you get when trying to connect! When you test your privileges, you should first run `mysqlaccess'. After this, execute `mysqladmin reload version' and try to connect with the program that gives you trouble. `mysqlaccess' can be found in the `bin' directory under your *MySQL* installation directory. * If you have a patch for a bug, that is good, but don't assume the patch is all we need, or that we will use it, if you don't provide some necessary information, such as test cases showing the bug that your patch fixes. We might find problems with your patch or we might not understand it at all; if so, we can't use it. If we can't verify exactly what the patch is meant for, we won't use it. Test cases will help us here. Show that the patch will handle all the situations that may occur. If we find a borderline case (even a rare one) where the patch won't work, it may be useless. * Guesses about what the bug is, why it occurs, or what it depends on, are usually wrong. Even the *MySQL* team can't guess such things without first using a debugger to determine the real cause of a bug. * Indicate in your mail message that you have checked the reference manual and mail archive so others know that you have tried to solve the problem yourself. * If you get a `parse error', please check your syntax closely! If you can't find something wrong with it, it's extremely likely that your current version of *MySQL* doesn't support the query you are using. If you are using the current version and the manual at `http://www.mysql.com/documentation/manual.php' doesn't cover the syntax you are using, *MySQL* doesn't support your query. In this case, your only options are to implement the syntax yourself or e-mail and ask for an offer to implement it! If the manual covers the syntax you are using, but you have an older version of *MySQL*, you should check the *MySQL* change history to see when the syntax was implemented. In this case, you have the option of upgrading to a newer version of *MySQL*. *Note News::. * If you have a problem such that your data appears corrupt or you get errors when you access some particular table, you should first check and then try repairing your tables with `myisamchk' or `CHECK TABLE' and `REPAIR TABLE'. *Note Maintenance::. * If you often get corrupted tables you should try to find out when and why this happens! In this case, the `mysql-data-directory/'hostname'.err' file may contain some information about what happened. *Note Error log::. Please include any relevant information from this file in your bug report! Normally `mysqld' should *NEVER* crash a table if nothing killed it in the middle of an update! If you can find the cause of `mysqld' dying, it's much easier for us to provide you with a fix for the problem! *Note What is crashing::. * If possible, download and install the most recent version of *MySQL* and check whether or not it solves your problem. All versions of *MySQL* are thoroughly tested and should work without problems! We believe in making everything as backward compatible as possible, and you should be able to switch *MySQL* versions in minutes! *Note Which version::. If you are a support customer, please cross-post the bug report to for higher priority treatment, as well as to the appropriate mailing list to see if someone else has experienced (and perhaps solved) the problem. For information on reporting bugs in *MyODBC*, see *Note ODBC Problems::. For solutions to some common problems, see *Note Problems::. When answers are sent to you individually and not to the mailing list, it is considered good etiquette to summarize the answers and send the summary to the mailing list so that others may have the benefit of responses you received that helped you solve your problem! Guidelines for Answering Question on the Mailing List ===================================================== If you consider your answer to have broad interest, you may want to post it to the mailing list instead of replying directly to the individual who asked. Try to make your answer general enough that people other than the original poster may benefit from it. When you post to the list, please make sure that your answer is not a duplication of a previous answer. Try to summarize the essential part of the question in your reply; don't feel obliged to quote the entire original message. Please don't post mail messages from your browser with HTML mode turned on! Many users don't read mail with a browser! MySQL Licensing and Support *************************** This chapter describes *MySQL* support and licensing arrangements: * The copyrights under which *MySQL* is distributed (*note Copyright::) * Sample situations illustrating when a license is required (*note Licensing examples::) * Support costs (*note Cost::) and support benefits (*note Support::) * Commercial licensing costs MySQL Licensing Policy ====================== The formal terms of the GPL license can be found at *Note GPL license::. Basically, our licensing policy and interpretation of the GPL is as follows: Note that older versions of *MySQL* are still using a more strict license (http://www.mysql.com/support/arrangements/mypl.html). See the documentation for that version for more information. If you need a commercial *MySQL* license, because the GPL license doesn't suit your application, you can buy one at `https://order.mysql.com/license.htmy'. For normal internal use, *MySQL* costs nothing. You do not have to pay us if you do not want to. A license is required if: - You link a part of the of *MySQL* that has a GPL Copyright to a program that is not free software (embedded usage of the *MySQL* server). In this case your application would also become GPL through the clause in the GPL license that acts as a virus. By licensing *MySQL* from us under a commercial license you will avoid this problem. - You have a commercial application that ONLY works with *MySQL* and ships the application with the *MySQL* server. This is because we view this as linking even if it is done over the network. - You have a distribution of *MySQL* and you don't provide the source code for your copy of the *MySQL* server, as defined in the GPL license. A license is *NOT* required if: - You do not need a license to include the client code in commercial programs. The client part of *MySQL* licensed with the LGPL `GNU Library General Public License'. The `mysql' command-line client includes code from the `readline' library that is under the `GPL'. - If your use of *MySQL* does not require a license, but you like *MySQL* and want to encourage further development, you are certainly welcome to purchase a license or *MySQL* support anyway. - If you use *MySQL* in a commercial context such that you profit by its use, we ask that you further the development of *MySQL* by purchasing some level of support. We feel that if *MySQL* helps your business, it is reasonable to ask that you help *MySQL*. (Otherwise, if you ask us support questions, you are not only using for free something into which we've put a lot a work, you're asking us to provide free support, too.) For circumstances under which a *MySQL* license is required, you need a license per machine that runs the `mysqld' server. However, a multiple-CPU machine counts as a single machine, and there is no restriction on the number of *MySQL* servers that run on one machine, or on the number of clients concurrently connected to a server running on that machine! If you have any questions as to whether or not a license is required for your particular use of *MySQL*, please read this again and then contact us. *Note Contact information::. If you require a *MySQL* license, the easiest way to pay for it is to use the license form on *MySQL*'s secure server at `https://order.mysql.com/license.htmy'. Other forms of payment are discussed in *Note Payment information::. Copyrights Used by MySQL ======================== There are several different copyrights on the *MySQL* distribution: 1. The *MySQL*-specific source needed to build the `mysqlclient' library is licensed under the `LGPL' and programs in the `client' directory is GPL. Each file has a header that shows which copyright is used for that file. 2. The client library and the (GNU `getopt') library are covered by the "GNU LIBRARY GENERAL PUBLIC LICENSE." *Note LGPL license::. 3. Some parts of the source (the `regexp' library) are covered by a Berkeley-style copyright. 4. All the source in the server and the (GNU `readline') library is covered by the "GNU GENERAL PUBLIC LICENSE." *Note GPL license::. This is also available as the file `COPYING' in the distributions. One goal is that the SQL client library should be free enough that it is possible to add *MySQL* support into commercial products without a license. For this reason, we chose the LGPL license for the client code. This means that you can use *MySQL* for free with any program that uses any of the free software licenses. *MySQL* is also free for any end user for his own or company usage. However, if you use *MySQL* for something important to you, you may want to help secure its development by purchasing licenses or a support contract. *Note Support::. Copyright Changes ----------------- Version 3.22 of *MySQL* is still using a more strict license. See the documentation for that version for more information. Example Licensing Situations ============================ This section describes some situations illustrating whether or not you must license the *MySQL* server. Generally these examples involve providing *MySQL* as an integral part of a product. Note that a single *MySQL* license covers any number of CPUs and `mysqld' servers on a machine! There is no artificial limit on the number of clients that connect to the server in any way. Selling Products that use MySQL ------------------------------- To determine whether or not you need a *MySQL* license when selling your application, you should ask whether the proper functioning of your application is dependent on the use of *MySQL* and whether you include the *MySQL* server with your product. There are several cases to consider: * Does your application require *MySQL* to function properly? * If your product requires *MySQL*, you need a license for any machine that runs the `mysqld' server. For example, if you've designed your application around *MySQL*, then you've really made a commercial product that requires the engine, so you need a license. * If your application does not require *MySQL*, you do not need to obtain a license. For example, if using *MySQL* just adds some new optional features to your product (such as adding logging to a database if *MySQL* is used rather than logging to a text file), it should fall within normal use, and a license would not be required. * In other words, you need a license if you sell a product designed specifically for use with *MySQL* or that requires the *MySQL* server to function at all. This is true whether or not you provide *MySQL* for your client as part of your product distribution. * It also depends on what you're doing for the client. Do you plan to provide your client with detailed instructions on installing *MySQL* with your software? Then your product may be contingent on the use of *MySQL*; if so, you need to buy a license. If you are simply tying into a database that you expect already to have been installed by the time your software is purchased, then you probably don't need a license. ISP MySQL Services ------------------ Internet Service Providers (ISPs) often host *MySQL* servers for their customers. With the GPL license this does not require a license. On the other hand, we do encourage people to use ISPs that have *MySQL* support, as this will give them the confidence that if they have some problem with their *MySQL* installation, their ISP will be able to solve the problem for them (in some cases with the help from the *MySQL* development team). All ISPs that want to keep themselves up-to-date should subscribe to our `announce' mailing list so that they can be aware of fatal issues that may be relevant for their *MySQL* installations. Note that if the ISP doesn't have a license for *MySQL*, it should give its customers at least read access to the source of the *MySQL* installation so that its customer can verify that it is patched correctly. Running a Web Server Using MySQL -------------------------------- If you use *MySQL* in conjunction with a Web server on Unix, you don't have to pay for a license. This is true even if you run a commercial Web server that uses *MySQL*, because you are not selling an embedded *MySQL* version yourself. However, in this case we would like you to purchase *MySQL* support, because *MySQL* is helping your enterprise. MySQL Licensing and Support Costs ================================= Our current license prices are shown below. These prices are now under review because of the change to a GPL copyright. New prices and terms will be posted on the *MySQL* web site at `http://www.mysql.com/' as soon as they are ready. All prices are in US Dollars. If you pay by credit card, the currency is EURO (European Union Euro) so the prices will differ slightly. *Number of licenses* *Per copy* *Total* 1 200 EURO 200 EURO 10 pack 150 EURO 1500 EURO 50 pack 120 EURO 6000 EURO For high volume (OEM) purchases, the following prices apply: *Number of *Per copy* *Minimum * *Minimum payment* licenses* 100-999 40 EURO 100 4000 EURO 1000-2499 25 EURO 200 5000 EURO 2500-4999 20 EURO 400 8000 EURO For OEM purchases, you must act as the middle-man for eventual problems or extension requests from your users. We also require that OEM customers have at least an extended e-mail support contract. Note that OEM licenses only apply for products where the user doesn't have direct access to the *MySQL* server (embedded system). In other words, the *MySQL* server should only be used with the application that was supplied you. If you have a low-margin, high-volume product, you can always talk to us about other terms (for example, a percent of the sale price). If you do, please be informative about your product, pricing, market, and any other information that may be relevant. A full-price license is not a support agreement and includes very minimal support. This means that we try to answer any relevant questions. If the answer is in the documentation, we will direct you to the appropriate section. If you have not purchased a license or support, we probably will not answer at all. If you discover what we consider a real bug, we are likely to fix it in any case. But if you pay for support we will notify you about the fix status instead of just fixing it in a later release. More comprehensive support is sold separately. Descriptions of what each level of support includes are given in *Note Support::. Costs for the various types of commercial support are shown below. Support level prices are in EURO (European Union Euro). One EURO is about 1.06 USD. *Type of support* *Cost per year* Basic e-mail support. *Note Basic EURO 200 email support::. Extended e-mail support *Note EURO 1000 Extended email support::. Login support *Note Login EURO 2000 support::. Extended login support *Note EURO 5000 Extended login support::. Telephone support *Note Telephone EURO 12000 support::. You may upgrade from any lower level of support to a higher level of support for the difference in price between the two support levels. We do also provide telephone support (mostly emergency support but also 24/7 support). This support option doesn't however have a fixed price but is negotiated for case to case. If you are interested in this option you can email and tell us about your needs. Note that as our sales staff is very busy, it may take some time until your request is handled. Our support staff does however always answer promptly to support questions! Payment information ------------------- Currently we can take SWIFT payments, checks, or credit cards. Payment should be made to: Postgirot Bank AB 105 06 STOCKHOLM, SWEDEN MySQL AB BOX 6434 11382 STOCKHOLM, SWEDEN SWIFT address: PGSI SESS Account number: 96 77 06 - 3 Specify: license and/or support and your name and e-mail address. In Europe and Japan you can use EuroGiro (that should be less expensive) to the same account. If you want to pay by check, make it payable to "MySQL Finland AB" and mail it to the address below: MySQL AB BOX 6434, Torsgatan 21 11382 STOCKHOLM, SWEDEN If you want to pay by credit card over the Internet, you can use MySQL AB's secure license form (https://order.mysql.com/license.htmy). You can also print a copy of the license form, fill it in, and send it by fax to: +46-8-729 69 05 If you want us to bill you, you can use the license form and write "bill us" in the comment field. You can also mail a message to (*not* `mysql@lists.mysql.com'!) with your company information and ask us to bill you. Contact Information ------------------- For commercial licensing, please contact the *MySQL* licensing team. The much preferred method is by e-mail to . Fax is also possible but handling of these may take much longer (Fax +46-8-729 69 05). If you represent a business that is interested in partnering with *MySQL*, please send e-mail to . For timely, precise answers to technical questions about *MySQL* you should order (https://order.mysql.com/) one of our support contracts (http://www.mysql.com/support/arrangements/types.html). *MySQL* support is provided by the *MySQL* developers so the standard is extremely high. If you are interested in placing a banner advertisement on our Web site, please send e-mail to . If you are interested in any of the jobs listed in our jobs (http://www.mysql.com/development/jobs/) section, please send e-mail to . For general discussion amongst our many users, please direct your attention to the appropriate mailing list (http://www.mysql.com/documentation/lists.html). For general information inquires, please send e-mail to . For questions or comments about the workings or content of the Web site, please send e-mail to . Types of Commercial Support =========================== The following is true of all support options: * The support is per year. * We will fix, or provide a reasonable workaround for any repeatable bug. * We will give a reasonable effort to find and fix any other MySQL related bug. * The higher level of support contract the more effort we will put into finding a solution to your problems. * The following is true for all support contracts except Basic email support: For non-bug related things, like helping you optimize your queries or your system, extending MySQL with new functionality, etc., we charge 200 EURO/hour, which is deducted from your support contract. In other words, if you have login support (2000 EURO), you can expect us to work up to 10 hours to help you with things like this. Basic E-mail Support -------------------- Basic e-mail support is a very inexpensive support option and should be thought of more as a way to support our development of *MySQL* than as a real support option. We at *MySQL* do give a lot of free support in all the different *MySQL* lists, and the money we get from basic e-mail support is largely used to make this possible. At this support level, the *MySQL* mailing lists are the preferred means of communication. Questions normally should be mailed to the primary mailing list () or one of the other regular lists (for example, for Windows-related *MySQL* questions), as someone else already may have experienced and solved the problem you have. *Note Asking questions::. However, by purchasing basic e-mail support, you also have access to the support address , which is not available as part of the minimal support that you get by purchasing a *MySQL* license. This means that for especially critical questions, you can cross-post your message to . (If the message contains sensitive data, you should post only to .) *REMEMBER!* to ALWAYS include your registration number and expiration date when you send a message to . Note that if you have encountered a critical, repeatable bug, and follow the rules outlined in the manual section of how to report bugs and send it to , we promise to try to fix this as soon as possible, regardless of your support level! *Note Bug reports::. Basic e-mail support includes the following types of service: * If your question is already answered in the manual, we will inform you of the correct section in which you can find the answer. If the answer is not in the manual, we will point you in the right direction to solve your problem. * We guarantee a timely answer for your e-mail messages. We can't guarantee that we can solve any problem, but at least you will receive an answer if we can contact you by e-mail. * We will help with unexpected problems when you install *MySQL* from a binary distribution on supported platforms. This level of support does not cover installing *MySQL* from a source distribution. Supported platforms are those for which *MySQL* is known to work. *Note Which OS::. * We will help you with bugs and missing features. Any bugs that are found are fixed for the next *MySQL* release. If the bug is critical for you, we will mail you a patch for it as soon the bug is fixed. Critical bugs always have the highest priority for us, and we ensure that they are fixed as soon as possible. * Your suggestions for the further development of *MySQL* will be taken into consideration. By taking email support you have already helped the further development of *MySQL*. If you want to have more input, upgrade to a higher level of support. * If you want us to help optimize your system, you must upgrade to a higher level of support. Extended E-mail Support ----------------------- Extended e-mail support includes everything in basic e-mail support with these additions: * Your e-mail will be dealt with before mail from basic e-mail support users and non-registered users. * Your suggestions for the further development of *MySQL* will receive strong consideration. Simple extensions that suit the basic goals of *MySQL* are implemented in a matter of days. By taking extended e-mail support you have already helped the further development of *MySQL*. * Typical situations that are covered by extended e-mail support are: - We will answer and (within reason) solve questions that relate to possible bugs in *MySQL*. As soon as the bug is found and corrected, we will mail a patch for it. - We will help with unexpected problems when you install *MySQL* from a source or binary distribution on supported platforms. - We will answer questions about missing features and offer hints how to work around them. - We will provide hints on optimizing `mysqld' for your situation. * You are allowed to influence the priority of items on the *MySQL* TODO List. *Note TODO::. This will ensure that the features you really need will be implemented sooner than they might be otherwise. Login Support ------------- Login support includes everything in extended e-mail support with these additions: * Your e-mail will be dealt with even before e-mail from extended e-mail support users. * Your suggestions for the further development of *MySQL* will be taken into very high consideration. Realistic extensions that can be implemented in a couple of hours and that suit the basic goals of *MySQL* will be implemented as soon as possible. * If you have a very specific problem, we can try to log in on your system to solve the problem "in place." * Like any database vendor, we can't guarantee that we can rescue any data from crashed tables, but if the worst happens, we will help you rescue as much as possible. *MySQL* has proven itself very reliable, but anything is possible due to circumstances beyond our control (for example, if your system crashes or someone kills the server by executing a `kill -9' command). * We will provide hints on optimizing your system and your queries. * You are allowed to call a *MySQL* developer (in moderation) and discuss your *MySQL*-related problems. This option is however only to be used as a last result during an emergency after we have failed to grasp the total problem with email. To make efficient use of our time we need to first get all facts about the problem, before talking on phone, to be able to work as efficiently as possible on solving the problem. Extended Login Support ---------------------- Extended login support includes everything in login support with these additions: * Your e-mail has the highest possible priority. * We will actively examine your system and help you optimize it and your queries. We may also optimize and/or extend *MySQL* to better suit your needs. * You may also request special extensions just for you. For example: mysql> select MY_FUNC(col1,col2) from table; * We will provide a binary distribution of all important *MySQL* releases for your system, as long as we can get an account on a similar system. In the worst case, we may require access to your system to be able to create a binary distribution. * If you can provide accommodations and pay for traveler fares, you can even get a *MySQL* developer to visit you and offer you help with your troubles. Extended login support entitles you to one personal encounter per year, but we are always very flexible towards our customers! If the visit takes 16 hours or more, the first 8 hours is without charge. For the hours above 8 hours, you will be charged with a rate that is at least 20 % less than our standard rates. Telephone Support ----------------- Telephone support includes everything in extended login support with these additions: * We will provide you with a dynamic web page showing the current list of `MySQL' developers that you can phone when you have a critical problem. * For non critical problem, you can request a *MySQL* developer to phone back within 48 hours to discuss `MySQL' related issues. Support for other table handlers -------------------------------- To get support for `BDB' tables, `InnoDB' tables or `GEMINI' tables you have to pay an additional 30% on the standard support price for each of the table handlers you would like to have support for. We at `MySQL AB' will help you create a proper bug report for the table handler and submit it to the developers for the specific table handler. We will also do our best to ensure that you will get a timely answer or solution from the developers of the table handler. Even if we are quite confident that we can solve most problems within a timely manner, we can't guarantee a quick solution for any problems you can get with the different table handlers. We will however do our best to help you get the problem solved. Installing MySQL **************** This chapter describes how to obtain and install *MySQL*: * For a list of sites from which you can obtain *MySQL*, see *Note Getting *MySQL*: Getting MySQL. * To see which platforms are supported, see *Note Which OS::. Please note that not all supported system are equally good for running *MySQL* on them. On some it is much more robust and efficient than others - see *Note Which OS:: for details. * Several versions of *MySQL* are available in both binary and source distributions. We also provide public access to our current source tree for those who want to see our most recent developments and help us test new code. To determine which version and type of distribution you should use, see *Note Which version::. When in doubt, use the binary distribution. * Installation instructions for binary and source distributions are described in *Note Installing binary:: and *Note Installing source::. Each set of instructions includes a section on system-specific problems you may run into. * For post-installation procedures, see *Note Post-installation::. These procedures apply whether you install *MySQL* using a binary or source distribution. How to Get MySQL ================ Check the *MySQL* home page (http://www.mysql.com/) for information about the current version and for downloading instructions. Our main download mirror is located at: `http://download.sourceforge.net/mirrors/mysql/' If you are interested in becoming a *MySQL* mirror site, you may anonymously rsync with: `rsync://download.sourceforge.net/mysql/'. Please send e-mail to notifying us of your mirror to be added to the list below. If you have problems downloading from our main site, try using one of the mirrors listed below. Please report bad or out-of-date mirrors to . *Europe:* * Austria [Univ. of Technology/Vienna] WWW (http://gd.tuwien.ac.at/db/mysql/) FTP (ftp://gd.tuwien.ac.at/db/mysql/) * Bulgaria [online.bg/Sofia] WWW (http://mysql.online.bg/) FTP (ftp://mysql.online.bg/) * Czech Republic [Masaryk University in Brno] WWW (http://mysql.linux.cz/index.html) FTP (ftp://ftp.fi.muni.cz/pub/mysql/) * Czech Republic [www.sopik.cz] WWW (http://www.mysql.cz/) * Czech Republic [www.gin.cz] WWW (http://mysql.gin.cz/) FTP (ftp://ftp.gin.cz/pub/MIRRORS/www.mysql.com/) * Denmark [Borsen] WWW (http://mysql.borsen.dk/) * Denmark [SunSITE] WWW (http://SunSITE.auc.dk/mysql/) FTP (ftp://SunSITE.auc.dk/pub/databases/mysql/) * Estonia [OKinteractive] WWW (http://mysql.mirror.ok.ee) * France [mtesa.net] WWW (http://mysql.mtesa.net/) * Finland [tonnikala.net] WWW (http://mysql.tonnikala.org/) * Germany [Kernelnotes.de, Bonn] WWW (http://www.kernelnotes.de/mysql/) FTP (ftp://ftp.kernelnotes.de/pub/mirror/mysql.org/) * Germany [Wolfenbuettel] WWW (http://www.fh-wolfenbuettel.de/ftp/pub/database/mysql/) FTP (ftp://ftp.fh-wolfenbuettel.de/pub/database/mysql/) * Greece [NTUA, Athens] WWW (http://www.ntua.gr/mysql/) FTP (ftp://ftp.ntua.gr/pub/databases/mysql/) * Hungary [Xenia] WWW (http://mysql.sote.hu/) FTP (ftp://xenia.sote.hu/pub/mirrors/www.mysql.com/) * Hungary [TiszaneT] WWW (http://mysql.tiszanet.hu/) FTP (ftp://mysql.tiszanet.hu/pub/mirrors/mysql/) * Iceland [GM] WWW (http://mysql.gm.is/) FTP (ftp://ftp.gm.is/pub/mysql/) * Italy [feelinglinux.com] WWW (http://mysql.feelinglinux.com/) * Italy [Teta Srl] WWW (http://www.teta.it/mysql/) * Italy [tzone.it] WWW (http://mysql.tzone.it/) * Ireland [Esat Net] WWW (http://ftp.esat.net/mirrors/download.sourceforge.net/pub/mirrors/mysql/) FTP (ftp://ftp.esat.net/mirrors/download.sourceforge.net/pub/mirrors/mysql/) * Latvia [linux.lv] FTP (ftp://ftp.linux.lv/pub/software/mysql/) * Netherlands [Silverpoint] WWW (http://mysql.silverpoint.nl/) * Netherlands [Widexs BV] WWW (http://mysql.widexs.nl/) FTP (ftp://mysql.widexs.nl/pub/mysql/) * Netherlands [ProServe] WWW (http://mysql.proserve.nl/) * Poland [Sunsite] WWW (http://sunsite.icm.edu.pl/mysql/) FTP (ftp://sunsite.icm.edu.pl/pub/unix/mysql/) * Poland [ncservice.com/Gdansk] WWW (http://mysql.service.net.pl/) * Portugal [Netc] WWW (http://ftp.netc.pt/pub/mysql/) FTP (ftp://ftp.netc.pt/pub/mysql/) * Romania [roedu.net/Bucharest] FTP (ftp://ftp.roedu.net/pub/mirrors/ftp.mysql.com/) * Russia [DirectNet] WWW (http://mysql.directnet.ru/) FTP (ftp://ftp.dn.ru/pub/MySQL/) * Russia [Scientific Center/Chernogolovka] FTP (ftp://ftp.chg.ru/pub/databases/mysql/) * Switzerland [Sunsite] WWW (http://sunsite.cnlab-switch.ch/ftp/mirror/mysql/) FTP (ftp://sunsite.cnlab-switch.ch/mirror/mysql/) * UK [Omnipotent/UK] WWW (http://mysql.omnipotent.net/) FTP (ftp://mysql.omnipotent.net/) * UK [PLiG/UK] WWW (http://ftp.plig.org/pub/mysql/) FTP (ftp://ftp.plig.org/pub/mysql/) * UK [Telekon Internet/UK] FTP (ftp://ftp.telekon.co.uk/pub/mysql/) * Ukraine [PACO] WWW (http://mysql.paco.net.ua) FTP (ftp://mysql.paco.net.ua/) * Ukraine [ISP Alkar Teleport/Dnepropetrovsk] WWW (http://mysql.dp.ua/) *North America:* * Canada [Tryc] WWW (http://web.tryc.on.ca/mysql/) * USA [Hurricane Electric/San Jose] WWW (http://mysql.he.net/) * USA [ValueClick, Los Angeles CA] WWW (http://mysql.valueclick.com/) FTP (ftp://mysql.valueclick.com/mysql/) * USA [Wisconsin University/Wisconsin] WWW (http://mirror.sit.wisc.edu/mysql/) FTP (ftp://mirror.sit.wisc.edu/mirrors/mysql/) * USA [LinuxWired/Scottsdale, AZ] WWW (http://mysql.linuxwired.net/) FTP (ftp://ftp.linuxwired.net/pub/mirrors/mysql/) * USA [adgrafix.com/Boston, MA] WWW (http://mysql.adgrafix.com/) *South America:* * Argentina [bannerlandia.com] WWW (http://mysql.bannerlandia.com.ar/) FTP (ftp://mysql.bannerlandia.com.ar/mirrors/mysql/) * Chile [Vision] WWW (http://mysql.vision.cl/) * Chile [PSINet] WWW (http://mysql.psinet.cl/) FTP (ftp://ftp.psinet.cl/pub/database/mysql/) * Chile [Tecnoera] WWW (http://mysql.tecnoera.com/) *Asia:* * China [Freecode] WWW (http://www.freecode.net.cn/mirror/mysql/) * China [linuxforum.net] WWW (http://www2.linuxforum.net/mirror/mysql/) * China [ISL/Hong Kong] WWW (http://mysql.islnet.net) * China [xcyber.org/Hong Kong] WWW (http://mysql.xcyber.org/) * South Korea [Webiiz] WWW (http://mysql.webiiz.com/) * South Korea [PanworldNet] WWW (http://mysql.holywar.net/) * Japan [Soft Agency] WWW (http://www.softagency.co.jp/MySQL) * Japan [u-aizu.ac.jp/Aizu] FTP (ftp://ftp.u-aizu.ac.jp/ftp/pub/dbms/mysql/mysql.com) * Singapore [HJC] WWW (http://mysql.hjc.edu.sg) FTP (ftp://ftp.hjc.edu.sg/mysql) * Taiwan [TTN] WWW (http://mysql.ttn.net) * Taiwan [nctu.edu/HsinChu] WWW (http://mysql.nctu.edu.tw/) *Australia:* * Australia [AARNet/Queensland] WWW (http://mysql.mirror.aarnet.edu.au/) FTP (ftp://mysql.mirror.aarnet.edu.au/) *Africa:* * South-Africa [Mweb] WWW (http://www.mysql.mweb.co.za/) * South Africa [The Internet Solution/Johannesburg] FTP (ftp://ftp.is.co.za/linux/mysql/) Operating Systems Supported by MySQL ==================================== We use GNU Autoconf, so it is possible to port *MySQL* to all modern systems with working Posix threads and a C++ compiler. (To compile only the client code, a C++ compiler is required but not threads.) We use and develop the software ourselves primarily on Sun Solaris (Versions 2.5 - 2.7) and SuSE Linux Version 7.x. Note that for many operating systems, the native thread support works only in the latest versions. *MySQL* has been reported to compile successfully on the following operating system/thread package combinations: * AIX 4.x with native threads. *Note IBM-AIX::. * Amiga. * BSDI 2.x with the included MIT-pthreads package. *Note BSDI::. * BSDI 3.0, 3.1 and 4.x with native threads. *Note BSDI::. * DEC Unix 4.x with native threads. *Note Alpha-DEC-UNIX::. * FreeBSD 2.x with the included MIT-pthreads package. *Note FreeBSD::. * FreeBSD 3.x and 4.x with native threads. *Note FreeBSD::. * HP-UX 10.20 with the included MIT-pthreads package. *Note HP-UX 10.20::. * HP-UX 11.x with the native threads. *Note HP-UX 11.x::. * Linux 2.0+ with LinuxThreads 0.7.1+ or `glibc' 2.0.7+. *Note Linux::. * Mac OS X Server. *Note Mac OS X::. * NetBSD 1.3/1.4 Intel and NetBSD 1.3 Alpha (Requires GNU make). *Note NetBSD::. * OpenBSD > 2.5 with native therads. OpenBSD < 2.5 with the included MIT-pthreads package. *Note OpenBSD::. * OS/2 Warp 3, FixPack 29 and OS/2 Warp 4, FixPack 4. *Note OS/2::. * SGI Irix 6.x with native threads. *Note SGI-Irix::. * Solaris 2.5 and above with native threads on SPARC and x86. *Note Solaris::. * SunOS 4.x with the included MIT-pthreads package. *Note Solaris::. * SCO OpenServer with a recent port of the FSU Pthreads package. *Note SCO::. * SCO UnixWare 7.0.1. *Note SCO Unixware::. * Tru64 Unix * Win95, Win98, NT, and Win2000. *Note Windows::. Note that not all platforms are suited equally well for running *MySQL*. How well a certain platform is suited for a high-load mission critical *MySQL* server is determined by the following factors: * General stability of the thread library. A platform may have excellent reputation otherwise, but if the thread library is unstable in the code that is called by *MySQL*, even if everything else is perfect, *MySQL* will be only as stable as the thread library. * The ability of the kernel and/or thread library to take advantage of *SMP* on multi-processor systems. In other words, when a process creates a thread, it should be possible for that thread to run on a different CPU than the original process. * The ability of the kernel and/or the thread library to run many threads which acquire/release a mutex over a short critical region frequently without excessive context switches. In other words, if the implementation of `pthread_mutex_lock()' is too anxious to yield CPU, this will hurt *MySQL* tremendously. If this issue is not taken care of, adding extra CPUs will actually make *MySQL* slower. * General file system stability/performance. * Ability of the file system to deal with large files at all and deal with them efficiently, if your tables are big. * Our level of expertise here at *MySQL AB* with the platform. If we know a platform well, we introduce platform-specific optimizations/fixes enabled at compile time. We can also provide advice on configuring your system optimally for *MySQL*. * The amount of testing of similar configurations we have done internally. * The number of users that have successfully run *MySQL* on that platform in similar configurations. If this number is high, the chances of hitting some platform-specific surprise are much smaller. Based on the above criteria, the best platforms for running *MySQL* at this point are x86 with SuSE Linux 7.1, 2.4 kernel and ReiserFS (or any similar Linux distribution) and Sparc with Solaris 2.7 or 2.8. FreeBSD comes third, but we really hope it will join the top club once the thread library is improved. We also hope that at some point we will be able to include all other platforms on which *MySQL* compiles, runs ok, but not quite with the same level of stability and performance, into the top category. This will require some effort on our part in cooperation with the developers of the OS/library components *MySQL* depends upon. If you are interested in making one of those components better, are in a position to influence their development, and need more detailed instructions on what *MySQL* needs to run better, send an e-mail to . Please note that the comparison above is not to say that one OS is better or worse than the other in general. We are talking about choosing a particular OS for a dedicated purpose - running *MySQL*, and compare platforms in that regard only. With this in mind, the result of this comparison would be different if we included more issues into it. And in some cases, the reason one OS is better than the other could simply be that we have put forth more effort into testing on and optimizing for that particular platform. We are just stating our observations to help you make a decision on which platform to use *MySQL* on in your setup. Which MySQL Version to Use ========================== The first decision to make is whether you want to use the latest development release or the last stable release: * Normally, if you are beginning to use *MySQL* for the first time or trying to port it to some system for which there is no binary distribution, we recommend going with the stable release (currently Version 3.23.39. Note that all *MySQL* releases are checked with the *MySQL* benchmarks and an extensive test suite before each release. * Otherwise, if you are running an old system and want to upgrade, but don't want to take chances with a non-seamless upgrade, you should upgrade to the latest in the same branch you are using (where only the last version number is newer than yours). We have tried to fix only fatal bugs and make small, relatively safe changes to that version. The second decision to make is whether you want to use a source distribution or a binary distribution. In most cases you should probably use a binary distribution, if one exists for your platform, as this generally will be easier to install than a source distribution. In the following cases you probably will be better off with a source installation: * If you want to install *MySQL* at some explicit location. (The standard binary distributions are "ready to run" at any place, but you may want to get even more flexibility). * To be able to satisfy different user requirements, we are providing two different binary versions; One compiled with the non-transactional table handlers, (a small, fast binary), and one configured with the most important extended options like transaction-safe tables. Both versions are compiled from the same source distribution. All native `MySQL' clients can connect to both *MySQL* versions. The extended *MySQL* binary distribution is marked with the `-max' suffix and is configured with the same options as `mysqld-max'. *Note `mysqld-max': mysqld-max. If you want to use the `MySQL-Max' RPM, you must first install the standard `MySQL' RPM. * If you want to configure `mysqld' with some extra feature that are NOT in the standard binary distributions. Here is a list of the most common extra options that you may want to use: * -with-berkeley-db * -with-innodb * -with-raid * -with-libwrap * -with-named-z-lib (This is done for some of the binaries) * -with-debug[=full] * The default binary distribution is normally compiled with support for all characters sets and should work on a variety of processors from the same processor family. If you want a faster *MySQL* server you may want to recompile it with support for only the character sets you need, use a better compiler (like `pgcc') or use compiler options that are better optimized for your processor. * If you have found a bug and reported it to the *MySQL* development team you will probably receive a patch that you need to apply to the source distribution to get the bug fixed. * If you want to read (and/or modify) the C and C++ code that makes up *MySQL*, you should get a source distribution. The source code is always the ultimate manual. Source distributions also contain more tests and examples than binary distributions. The *MySQL* naming scheme uses release numbers that consist of three numbers and a suffix. For example, a release name like `mysql-3.21.17-beta' is interpreted like this: * The first number (`3') describes the file format. All Version 3 releases have the same file format. * The second number (`21') is the release level. Normally there are two to choose from. One is the release/stable branch (currently `23') and the other is the development branch (currently `4.0'). Normally both are stable, but the development version may have quirks, missing documentation on new features, or may fail to compile on some systems. * The third number (`17') is the version number within the release level. This is incremented for each new distribution. Usually you want the latest version for the release level you have chosen. * The suffix (`beta') indicates the stability level of the release. The possible suffixes are: - `alpha' indicates that the release contains some large section of new code that hasn't been 100% tested. Known bugs (usually there are none) should be documented in the News section. *Note News::. There are also new commands and extensions in most alpha releases. Active development that may involve major code changes can occur on an alpha release, but everything will be tested before doing a release. There should be no known bugs in any *MySQL* release. - `beta' means that all new code has been tested. No major new features that could cause corruption on old code are added. There should be no known bugs. A version changes from alpha to beta when there haven't been any reported fatal bugs within an alpha version for at least a month and we don't plan to add any features that could make any old command more unreliable. - `gamma' is a beta that has been around a while and seems to work fine. Only minor fixes are added. This is what many other companies call a release. - If there is no suffix, it means that the version has been run for a while at many different sites with no reports of bugs other than platform-specific bugs. Only critical bug fixes are applied to the release. This is what we call a stable release. All versions of *MySQL* are run through our standard tests and benchmarks to ensure that they are relatively safe to use. Because the standard tests are extended over time to check for all previously found bugs, the test suite keeps getting better. Note that all releases have been tested at least with: An internal test suite This is part of a production system for a customer. It has many tables with hundreds of megabytes of data. The *MySQL* benchmark suite This runs a range of common queries. It is also a test to see whether the latest batch of optimizations actually made the code faster. *Note Benchmarks::. The `crash-me' test This tries to determine what features the database supports and what its capabilities and limitations are. *Note Benchmarks::. Another test is that we use the newest *MySQL* version in our internal production environment, on at least one machine. We have more than 100 gigabytes of data to work with. How and When Updates Are Released ================================= *MySQL* is evolving quite rapidly here at *MySQL AB* and we want to share this with other *MySQL* users. We try to make a release when we have very useful features that others seem to have a need for. We also try to help out users who request features that are easy to implement. We take note of what our licensed users want to have, and we especially take note of what our extended e-mail supported customers want and try to help them out. No one has to download a new release. The News section will tell you if the new release has something you really want. *Note News::. We use the following policy when updating *MySQL*: * For each minor update, the last number in the version string is incremented. When there are major new features or minor incompatibilities with previous versions, the second number in the version string is incremented. When the file format changes, the first number is increased. * Stable tested releases are meant to appear about 1-2 times a year, but if small bugs are found, a release with only bug fixes will be released. * Working releases are meant to appear about every 1-8 weeks. * Binary distributions for some platforms will be made by us for major releases. Other people may make binary distributions for other systems but probably less frequently. * We usually make patches available as soon as we have located and fixed small bugs. * For non-critical but annoying bugs, we will make patches available if they are sent to us. Otherwise we will combine many of them into a larger patch. * If there is, by any chance, a fatal bug in a release we will make a new release as soon as possible. We would like other companies to do this, too. The current stable release is Version 3.23; We have already moved active development to Version 4.0. Bugs will still be fixed in the stable version. We don't believe in a complete freeze, as this also leaves out bug fixes and things that "must be done." "Somewhat frozen" means that we may add small things that "almost surely will not affect anything that's already working." Installation Layouts ==================== This section describes the default layout of the directories created by installing binary and source distributions. A binary distribution is installed by unpacking it at the installation location you choose (typically `/usr/local/mysql') and creates the following directories in that location: *Directory* *Contents of directory* `bin' Client programs and the `mysqld' server `data' Log files, databases `include' Include (header) files `lib' Libraries `scripts' `mysql_install_db' `share/mysql' Error message files `sql-bench' Benchmarks A source distribution is installed after you configure and compile it. By default, the installation step installs files under `/usr/local', in the following subdirectories: *Directory* *Contents of directory* `bin' Client programs and scripts `include/mysql' Include (header) files `info' Documentation in Info format `lib/mysql' Libraries `libexec' The `mysqld' server `share/mysql' Error message files `sql-bench' Benchmarks and `crash-me' test `var' Databases and log files Within an installation directory, the layout of a source installation differs from that of a binary installation in the following ways: * The `mysqld' server is installed in the `libexec' directory rather than in the `bin' directory. * The data directory is `var' rather than `data'. * `mysql_install_db' is installed in the `/usr/local/bin' directory rather than in `/usr/local/mysql/scripts'. * The header file and library directories are `include/mysql' and `lib/mysql' rather than `include' and `lib'. You can create your own binary installation from a compiled source distribution by executing the script `scripts/make_binary_distribution'. Installing a MySQL Binary Distribution ====================================== You need the following tools to install a *MySQL* binary distribution: * GNU `gunzip' to uncompress the distribution. * A reasonable `tar' to unpack the distribution. GNU `tar' is known to work. Sun `tar' is known to have problems. An alternative installation method under Linux is to use RPM (RedHat Package Manager) distributions. *Note Linux-RPM::. If you run into problems, *PLEASE ALWAYS USE* `mysqlbug' when posting questions to . Even if the problem isn't a bug, `mysqlbug' gathers system information that will help others solve your problem. By not using `mysqlbug', you lessen the likelihood of getting a solution to your problem! You will find `mysqlbug' in the `bin' directory after you unpack the distribution. *Note Bug reports::. The basic commands you must execute to install and use a *MySQL* binary distribution are: shell> groupadd mysql shell> useradd -g mysql mysql shell> cd /usr/local shell> gunzip < /path/to/mysql-VERSION-OS.tar.gz | tar xvf - shell> ln -s mysql-VERSION-OS mysql shell> cd mysql shell> scripts/mysql_install_db shell> chown -R root /usr/local/mysql shell> chown -R mysql /usr/local/mysql/data shell> chgrp -R mysql /usr/local/mysql shell> chown -R root /usr/local/mysql/bin/ shell> bin/safe_mysqld --user=mysql & You can add new users using the `bin/mysql_setpermission' script if you install the `DBI' and `Msql-Mysql-modules' Perl modules. A more detailed description follows. To install a binary distribution, follow the steps below, then proceed to *Note Post-installation::, for post-installation setup and testing: 1. Pick the directory under which you want to unpack the distribution, and move into it. In the example below, we unpack the distribution under `/usr/local' and create a directory `/usr/local/mysql' into which *MySQL* is installed. (The following instructions therefore assume you have permission to create files in `/usr/local'. If that directory is protected, you will need to perform the installation as `root'.) 2. Obtain a distribution file from one of the sites listed in *Note Getting *MySQL*: Getting MySQL. *MySQL* binary distributions are provided as compressed `tar' archives and have names like `mysql-VERSION-OS.tar.gz', where `VERSION' is a number (for example, `3.21.15'), and `OS' indicates the type of operating system for which the distribution is intended (for example, `pc-linux-gnu-i586'). 3. If you see a binary distribution marked with the `-max' prefix, this means that the binary has support for transaction-safe tables and other features. *Note `mysqld-max': mysqld-max. Note that all binaries are built from the same *MySQL* source distribution. 4. Add a user and group for `mysqld' to run as: shell> groupadd mysql shell> useradd -g mysql mysql These commands add the `mysql' group and the `mysql' user. The syntax for `useradd' and `groupadd' may differ slightly on different versions of Unix. They may also be called `adduser' and `addgroup'. You may wish to call the user and group something else instead of `mysql'. 5. Change into the intended installation directory: shell> cd /usr/local 6. Unpack the distribution and create the installation directory: shell> gunzip < /path/to/mysql-VERSION-OS.tar.gz | tar xvf - shell> ln -s mysql-VERSION-OS mysql The first command creates a directory named `mysql-VERSION-OS'. The second command makes a symbolic link to that directory. This lets you refer more easily to the installation directory as `/usr/local/mysql'. 7. Change into the installation directory: shell> cd mysql You will find several files and subdirectories in the `mysql' directory. The most important for installation purposes are the `bin' and `scripts' subdirectories. `bin' This directory contains client programs and the server You should add the full pathname of this directory to your `PATH' environment variable so that your shell finds the *MySQL* programs properly. *Note Environment variables::. `scripts' This directory contains the `mysql_install_db' script used to initialize the `mysql' database containing the grant tables that store the server access permissions. 8. If you would like to use `mysqlaccess' and have the *MySQL* distribution in some non-standard place, you must change the location where `mysqlaccess' expects to find the `mysql' client. Edit the `bin/mysqlaccess' script at approximately line 18. Search for a line that looks like this: $MYSQL = '/usr/local/bin/mysql'; # path to mysql executable Change the path to reflect the location where `mysql' actually is stored on your system. If you do not do this, you will get a `Broken pipe' error when you run `mysqlaccess'. 9. Create the *MySQL* grant tables (necessary only if you haven't installed *MySQL* before): shell> scripts/mysql_install_db Note that *MySQL* versions older than Version 3.22.10 started the *MySQL* server when you run `mysql_install_db'. This is no longer true! 10. Change ownership of binaries to `root' and ownership of the data directory to the user that you will run `mysqld' as: shell> chown -R root /usr/local/mysql shell> chown -R mysql /usr/local/mysql/var shell> chgrp -R mysql /usr/local/mysql The first command changes the `owner' attribute of the files to the `root' user, the second one changes the `owner' attribute of the data directory to the `mysql' user, and the third one changes the `group' attribute to the `mysql' group. 11. If you want to install support for the Perl `DBI'/`DBD' interface, see *Note Perl support::. 12. If you would like *MySQL* to start automatically when you boot your machine, you can copy `support-files/mysql.server' to the location where your system has its startup files. More information can be found in the `support-files/mysql.server' script itself and in *Note Automatic start::. After everything has been unpacked and installed, you should initialize and test your distribution. You can start the *MySQL* server with the following command: shell> bin/safe_mysqld --user=mysql & *Note `safe_mysqld': safe_mysqld. *Note Post-installation::. Linux RPM Notes --------------- The recommended way to install *MySQL* on Linux is by using an RPM file. The *MySQL* RPMs are currently being built on a RedHat Version 6.2 system but should work on other versions of Linux that support `rpm' and use `glibc'. If you have problems with an RPM file, for example, if you receive the error "`Sorry, the host 'xxxx' could not be looked up'", see *Note Binary notes-Linux::. The RPM files you may want to use are: * `MySQL-VERSION.i386.rpm' The *MySQL* server. You will need this unless you only want to connect to a *MySQL* server running on another machine. * `MySQL-client-VERSION.i386.rpm' The standard *MySQL* client programs. You probably always want to install this package. * `MySQL-bench-VERSION.i386.rpm' Tests and benchmarks. Requires Perl and msql-mysql-modules RPMs. * `MySQL-devel-VERSION.i386.rpm' Libraries and include files needed if you want to compile other *MySQL* clients, such as the Perl modules. * `MySQL-VERSION.src.rpm' This contains the source code for all of the above packages. It can also be used to try to build RPMs for other architectures (for example, Alpha or SPARC). To see all files in an RPM package, run: shell> rpm -qpl MySQL-VERSION.i386.rpm To perform a standard minimal installation, run: shell> rpm -i MySQL-VERSION.i386.rpm MySQL-client-VERSION.i386.rpm To install just the client package, run: shell> rpm -i MySQL-client-VERSION.i386.rpm The RPM places data in `/var/lib/mysql'. The RPM also creates the appropriate entries in `/etc/rc.d/' to start the server automatically at boot time. (This means that if you have performed a previous installation, you may want to make a copy of your previously installed *MySQL* startup file if you made any changes to it, so you don't lose your changes.) After installing the RPM file(s), the `mysqld' daemon should be running and you should now be able to start using *MySQL*. *Note Post-installation::. If something goes wrong, you can find more information in the binary installation chapter. *Note Installing binary::. Building Client Programs ------------------------ If you compile *MySQL* clients that you've written yourself or that you obtain from a third party, they must be linked using the `-lmysqlclient -lz' option on the link command. You may also need to specify a `-L' option to tell the linker where to find the library. For example, if the library is installed in `/usr/local/mysql/lib', use `-L/usr/local/mysql/lib -lmysqlclient -lz' on the link command. For clients that use *MySQL* header files, you may need to specify a `-I' option when you compile them (for example, `-I/usr/local/mysql/include'), so the compiler can find the header files. System-specific Issues ---------------------- The following sections indicate some of the issues that have been observed on particular systems when installing *MySQL* from a binary distribution or from RPM files. Linux Notes for Binary Distributions .................................... *MySQL* needs at least Linux Version 2.0. The binary release is linked with `-static', which means you do not normally need to worry about which version of the system libraries you have. You need not install LinuxThreads, either. A program linked with `-static' is slightly bigger than a dynamically linked program but also slightly faster (3-5%). One problem, however, is that you can't use user-definable functions (UDFs) with a statically linked program. If you are going to write or use UDF functions (this is something only for C or C++ programmers), you must compile *MySQL* yourself, using dynamic linking. If you are using a `libc'-based system (instead of a `glibc2' system), you will probably get some problems with hostname resolving and `getpwnam()' with the binary release. (This is because `glibc' unfortunately depends on some external libraries to resolve hostnames and `getpwent()', even when compiled with `-static'). In this case you probably get the following error message when you run `mysql_install_db': Sorry, the host 'xxxx' could not be looked up or the following error when you try to run `mysqld' with the `--user' option: getpwnam: No such file or directory You can solve this problem in one of the following ways: * Get a *MySQL* source distribution (an RPM or the `tar.gz' distribution) and install this instead. * Execute `mysql_install_db --force'; This will not execute the `resolveip' test in `mysql_install_db'. The downside is that you can't use host names in the grant tables; you must use IP numbers instead (except for `localhost'). If you are using an old *MySQL* release that doesn't support `--force', you have to remove the `resolveip' test in `mysql_install' with an editor. * Start `mysqld' with `su' instead of using `--user'. The Linux-Intel binary and RPM releases of *MySQL* are configured for the highest possible speed. We are always trying to use the fastest stable compiler available. *MySQL* Perl support requires Version Perl 5.004_03 or newer. On some Linux 2.2 versions, you may get the error `Resource temporarily unavailable' when you do a lot of new connections to a `mysqld' server over TCP/IP. The problem is that Linux has a delay between when you close a TCP/IP socket and until this is actually freed by the system. As there is only room for a finite number of TCP/IP slots, you will get the above error if you try to do too many new TCP/IP connections during a small time, like when you run the *MySQL* `test-connect' benchmark over TCP/IP. We have mailed about this problem a couple of times to different Linux mailing lists but have never been able to resolve this properly. The only known 'fix' to this problem is to use persistent connections in your clients or use sockets, if you are running the database server and clients on the same machine. We hope that the `Linux 2.4' kernel will fix this problem in the future. HP-UX Notes for Binary Distributions .................................... Some of the binary distributions of *MySQL* for HP-UX is distributed as an HP depot file and as a tar file. To use the depot file you must be running at least HP-UX 10.x to have access to HP's software depot tools. The HP version of *MySQL* was compiled on an HP 9000/8xx server under HP-UX 10.20, and uses MIT-pthreads. It is known to work well under this configuration. *MySQL* Version 3.22.26 and newer can also be built with HP's native thread package. Other configurations that may work: * HP 9000/7xx running HP-UX 10.20+ * HP 9000/8xx running HP-UX 10.30 The following configurations almost definitely won't work: * HP 9000/7xx or 8xx running HP-UX 10.x where x < 2 * HP 9000/7xx or 8xx running HP-UX 9.x To install the distribution, use one of the commands below, where `/path/to/depot' is the full pathname of the depot file: * To install everything, including the server, client and development tools: shell> /usr/sbin/swinstall -s /path/to/depot mysql.full * To install only the server: shell> /usr/sbin/swinstall -s /path/to/depot mysql.server * To install only the client package: shell> /usr/sbin/swinstall -s /path/to/depot mysql.client * To install only the development tools: shell> /usr/sbin/swinstall -s /path/to/depot mysql.developer The depot places binaries and libraries in `/opt/mysql' and data in `/var/opt/mysql'. The depot also creates the appropriate entries in `/etc/init.d' and `/etc/rc2.d' to start the server automatically at boot time. Obviously, this entails being `root' to install. To install the HP-UX tar.gz distribution, you must have a copy of GNU `tar'. Installing a MySQL Source Distribution ====================================== Before you proceed with the source installation, check first to see if our binary is available for your platform and if it will work for you. We put in a lot of effort into making sure that our binaries are built with the best possible options. You need the following tools to build and install *MySQL* from source: * GNU `gunzip' to uncompress the distribution. * A reasonable `tar' to unpack the distribution. GNU `tar' is known to work. Sun `tar' is known to have problems. * A working ANSI C++ compiler. `gcc' >= 2.95.2, `egcs' >= 1.0.2 or `egcs 2.91.66', SGI C++, and SunPro C++ are some of the compilers that are known to work. `libg++' is not needed when using `gcc'. `gcc' 2.7.x has a bug that makes it impossible to compile some perfectly legal C++ files, such as `sql/sql_base.cc'. If you only have `gcc' 2.7.x, you must upgrade your `gcc' to be able to compile *MySQL*. `gcc' 2.8.1 is also known to have problems on some platforms so it should be avoided if there exists a new compiler for the platform.. `gcc' >= 2.95.2 is recommended when compiling *MySQL* Version 3.23.x. * A good `make' program. GNU `make' is always recommended and is sometimes required. If you have problems, we recommend trying GNU `make' 3.75 or newer. If you are using a recent version of *gcc*, recent enough to understand `-fno-exceptions' option, it is *VERY IMPORTANT* that you use it. Otherwise, you may compile a binary that crashes randomly. We also recommend that you use `-felide-contructors' and `-fno-rtti' along with `-fno-exceptions'. When in doubt, do the following: CFLAGS="-O3" CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static On most systems this will give you a fast and stable binary. If you run into problems, *PLEASE ALWAYS USE `mysqlbug'* when posting questions to . Even if the problem isn't a bug, `mysqlbug' gathers system information that will help others solve your problem. By not using `mysqlbug', you lessen the likelihood of getting a solution to your problem! You will find `mysqlbug' in the `scripts' directory after you unpack the distribution. *Note Bug reports::. Quick Installation Overview --------------------------- The basic commands you must execute to install a *MySQL* source distribution are: shell> groupadd mysql shell> useradd -g mysql mysql shell> gunzip < mysql-VERSION.tar.gz | tar -xvf - shell> cd mysql-VERSION shell> ./configure --prefix=/usr/local/mysql shell> make shell> make install shell> scripts/mysql_install_db shell> chown -R root /usr/local/mysql shell> chown -R mysql /usr/local/mysql/var shell> chgrp -R mysql /usr/local/mysql shell> cp support-files/my-medium.cnf /etc/my.cnf shell> /usr/local/mysql/bin/safe_mysqld --user=mysql & If you want have support for InnoDB tables, you should edit the `/etc/my.cnf' file and remove the `#' character before the parameters that starts with `innodb_...'. *Note Option files::. *Note InnoDB start::. If you start from a source RPM, then do the following: shell> rpm --rebuild MySQL-VERSION.src.rpm This will make a binary RPM that you can install. You can add new users using the `bin/mysql_setpermission' script if you install the `DBI' and `Msql-Mysql-modules' Perl modules. A more detailed description follows. To install a source distribution, follow the steps below, then proceed to *Note Post-installation::, for post-installation initialization and testing: 1. Pick the directory under which you want to unpack the distribution, and move into it. 2. Obtain a distribution file from one of the sites listed in *Note Getting *MySQL*: Getting MySQL. 3. If you are interested in using Berkeley DB tables with MySQL, you will need to obtain a patched version of the Berkeley DB source code. Please read the chapter on Berkeley DB tables before proceeding. *Note BDB::. *MySQL* source distributions are provided as compressed `tar' archives and have names like `mysql-VERSION.tar.gz', where `VERSION' is a number like 3.23.39. 4. Add a user and group for `mysqld' to run as: shell> groupadd mysql shell> useradd -g mysql mysql These commands add the `mysql' group, and the `mysql' user. The syntax for `useradd' and `groupadd' may differ slightly on different versions of Unix. They may also be called `adduser' and `addgroup'. You may wish to call the user and group something else instead of `mysql'. 5. Unpack the distribution into the current directory: shell> gunzip < /path/to/mysql-VERSION.tar.gz | tar xvf - This command creates a directory named `mysql-VERSION'. 6. Change into the top-level directory of the unpacked distribution: shell> cd mysql-VERSION Note that currently you must configure and build *MySQL* from this top-level directory. You can not build it in a different directory. 7. Configure the release and compile everything: shell> ./configure --prefix=/usr/local/mysql shell> make When you run `configure', you might want to specify some options. Run `./configure --help' for a list of options. *Note `configure' options: configure options, discusses some of the more useful options. If `configure' fails, and you are going to send mail to to ask for assistance, please include any lines from `config.log' that you think can help solve the problem. Also include the last couple of lines of output from `configure' if `configure' aborts. Post the bug report using the `mysqlbug' script. *Note Bug reports::. If the compile fails, see *Note Compilation problems::, for help with a number of common problems. 8. Install everything: shell> make install You might need to run this command as `root'. 9. Create the *MySQL* grant tables (necessary only if you haven't installed *MySQL* before): shell> scripts/mysql_install_db Note that *MySQL* versions older than Version 3.22.10 started the *MySQL* server when you run `mysql_install_db'. This is no longer true! 10. Change ownership of binaries to `root' and ownership of the data directory to the user that you will run `mysqld' as: shell> chown -R root /usr/local/mysql shell> chown -R mysql /usr/local/mysql/var shell> chgrp -R mysql /usr/local/mysql The first command changes the `owner' attribute of the files to the `root' user, the second one changes the `owner' attribute of the data directory to the `mysql' user, and the third one changes the `group' attribute to the `mysql' group. 11. If you want to install support for the Perl `DBI'/`DBD' interface, see *Note Perl support::. 12. If you would like *MySQL* to start automatically when you boot your machine, you can copy `support-files/mysql.server' to the location where your system has its startup files. More information can be found in the `support-files/mysql.server' script itself and in *Note Automatic start::. After everything has been installed, you should initialize and test your distribution: shell> /usr/local/mysql/bin/safe_mysqld --user=mysql & If that command fails immediately with `mysqld daemon ended' then you can find some information in the file `mysql-data-directory/'hostname'.err'. The likely reason is that you already have another `mysqld' server running. *Note Multiple servers::. *Note Post-installation::. Applying Patches ---------------- Sometimes patches appear on the mailing list or are placed in the patches area (http://www.mysql.com/Downloads/Patches) of the *MySQL* Web site. To apply a patch from the mailing list, save the message in which the patch appears in a file, change into the top-level directory of your *MySQL* source tree, and run these commands: shell> patch -p1 < patch-file-name shell> rm config.cache shell> make clean Patches from the FTP site are distributed as plain text files or as files compressed with `gzip'. Apply a plain patch as shown above for mailing list patches. To apply a compressed patch, change into the top-level directory of your *MySQL* source tree and run these commands: shell> gunzip < patch-file-name.gz | patch -p1 shell> rm config.cache shell> make clean After applying a patch, follow the instructions for a normal source install, beginning with the `./configure' step. After running the `make install' step, restart your *MySQL* server. You may need to bring down any currently running server before you run `make install'. (Use `mysqladmin shutdown' to do this.) Some systems do not allow you to install a new version of a program if it replaces the version that is currently executing. Typical `configure' Options --------------------------- The `configure' script gives you a great deal of control over how you configure your *MySQL* distribution. Typically you do this using options on the `configure' command line. You can also affect `configure' using certain environment variables. *Note Environment variables::. For a list of options supported by `configure', run this command: shell> ./configure --help Some of the more commonly-used `configure' options are described below: * To compile just the *MySQL* client libraries and client programs and not the server, use the `--without-server' option: shell> ./configure --without-server If you don't have a C++ compiler, `mysql' will not compile (it is the one client program that requires C++). In this case, you can remove the code in `configure' that tests for the C++ compiler and then run `./configure' with the `--without-server' option. The compile step will still try to build `mysql', but you can ignore any warnings about `mysql.cc'. (If `make' stops, try `make -k' to tell it to continue with the rest of the build even if errors occur.) * If you don't want your log files and database directories located under `/usr/local/var', use a `configure' command, something like one of these: shell> ./configure --prefix=/usr/local/mysql shell> ./configure --prefix=/usr/local \ --localstatedir=/usr/local/mysql/data The first command changes the installation prefix so that everything is installed under `/usr/local/mysql' rather than the default of `/usr/local'. The second command preserves the default installation prefix, but overrides the default location for database directories (normally `/usr/local/var') and changes it to `/usr/local/mysql/data'. * If you are using Unix and you want the *MySQL* socket located somewhere other than the default location (normally in the directory `/tmp' or `/var/run') use a `configure' command like this: shell> ./configure --with-unix-socket-path=/usr/local/mysql/tmp/mysql.sock Note that the given file must be an absolute pathname! * If you want to compile statically linked programs (for example, to make a binary distribution, to get more speed, or to work around problems with some RedHat Linux distributions), run `configure' like this: shell> ./configure --with-client-ldflags=-all-static \ --with-mysqld-ldflags=-all-static * If you are using `gcc' and don't have `libg++' or `libstdc++' installed, you can tell `configure' to use `gcc' as your C++ compiler: shell> CC=gcc CXX=gcc ./configure When you use `gcc' as your C++ compiler, it will not attempt to link in `libg++' or `libstdc++'. Here is some common environment variables to set depending on the compiler you are using: gcc 2.7.2.1 CC=gcc CXX=gcc CXXFLAGS="-O3 -felide-constructors" egcs 1.0.3a CC=gcc CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" gcc 2.95.2 CFLAGS="-O3 -mpentiumpro" CXX=gcc CXXFLAGS="-O3 -mpentiumpro -felide-constructors -fno-exceptions -fno-rtti" pgcc 2.90.29 CFLAGS="-O3 -mpentiumpro -mstack-align-double" or newer CXX=gcc CXXFLAGS="-O3 -mpentiumpro -mstack-align-double -felide-constructors -fno-exceptions -fno-rtti" In most cases you can get a reasonably optimal *MySQL* binary by using the options from the above and adding the following options to the configure line: --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static The full configure line would in other words be something like the following for all recent gcc versions: CFLAGS="-O3 -mpentiumpro" CXX=gcc CXXFLAGS="-O3 -mpentiumpro -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static The binaries we provide on the *MySQL* Web site at `http://www.mysql.com' are all compiled with full optimization and should be perfect for most users. *Note MySQL binaries::. There are some things you can tweak to make an even faster binary, but this is only for advanced users. *Note Compile and link options::. If the build fails and produces errors about your compiler or linker not being able to create the shared library `libmysqlclient.so.#' (`#' is a version number), you can work around this problem by giving the `--disable-shared' option to `configure'. In this case, `configure' will not build a shared `libmysqlclient.so.#' library. * You can configure *MySQL* not to use `DEFAULT' column values for non-`NULL' columns (that is, columns that are not allowed to be `NULL'). This causes `INSERT' statements to generate an error unless you explicitly specify values for all columns that require a non-`NULL' value. To suppress use of default values, run `configure' like this: shell> CXXFLAGS=-DDONT_USE_DEFAULT_FIELDS ./configure * By default, *MySQL* uses the ISO-8859-1 (Latin1) character set. To change the default set, use the `--with-charset' option: shell> ./configure --with-charset=CHARSET `CHARSET' may be one of `big5', `cp1251', `cp1257', `czech', `danish', `dec8', `dos', `euc_kr', `gb2312', `gbk', `german1', `hebrew', `hp8', `hungarian', `koi8_ru', `koi8_ukr', `latin1', `latin2', `sjis', `swe7', `tis620', `ujis', `usa7', or `win1251ukr'. *Note Character sets::. If you want to convert characters between the server and the client, you should take a look at the `SET OPTION CHARACTER SET' command. *Note `SET OPTION': SET OPTION. *Warning:* If you change character sets after having created any tables, you will have to run `myisamchk -r -q' on every table. Your indexes may be sorted incorrectly otherwise. (This can happen if you install *MySQL*, create some tables, then reconfigure *MySQL* to use a different character set and reinstall it.) * To configure *MySQL* with debugging code, use the `--with-debug' option: shell> ./configure --with-debug This causes a safe memory allocator to be included that can find some errors and that provides output about what is happening. *Note Debugging server::. * If your client programs are using threads, you need to also compile a thread-safe version of the *MySQL* client library with the `--with-thread-safe-client' configure options. This will create a `libmysqlclient_r' library with which you should link your threaded applications. *Note Thread-safe clients::. * Options that pertain to particular systems can be found in the system-specific sections later in this chapter. *Note Source install system issues::. Installing from the Development Source Tree =========================================== *CAUTION:* You should read this section only if you are interested in helping us test our new code. If you just want to get *MySQL* up and running on your system, you should use a standard release distribution (either a source or binary distribution will do). To obtain our most recent development source tree, use these instructions: 1. Download *BitKeeper* from `http://www.bitmover.com/cgi-bin/download.cgi'. You will need *Bitkeeper* 2.0 or newer to access our repository. 2. Follow the instructions to install it. 3. After *BitKeeper* is installed, use this command if you want to clone the *MySQL* 3.23 branch: shell> bk clone bk://work.mysql.com:7000 mysql To clone the 4.0 branch, use this command instead: shell> bk clone bk://work.mysql.com:7001 mysql-4.0 The initial download of the source tree may take a while, depending on the speed of your connection; be patient. 4. You will need GNU `autoconf', `automake', `libtool', and `m4' to run the next set of commands. If you get some strange error during this stage, check that you really have `libtool' installed! shell> cd mysql shell> bk -r edit shell> aclocal; autoheader; autoconf; automake; shell> ./configure # Add your favorite options here shell> make A collection of our standard configure scripts is located in the `BUILD/' subdirectory. If you are lazy, you can use `BUILD/compile-pentium-debug'. It will actually work on a lot of non-x86 machines despite its name. 5. When the build is done, run `make install'. Be careful with this on a production machine; the command may overwrite your live release installation. If you have another installation of *MySQL*, we recommand that you run `./configure' with different values for the `prefix', `tcp-port', and `unix-socket-path' options than those used for your production server. 6. Play hard with your new installation and try to make the new features crash. Start by running `make test'. *Note MySQL test suite::. 7. If you have gotten to the `make' stage and the distribution does not compile, please report it to . If you have installed the latest versions of the required GNU tools, and they crash trying to process our configuration files, please report that also. However, if you execute `aclocal' and get a `command not found' error or a similar problem, do not report it. Instead, make sure all the necessary tools are installed and that your `PATH' variable is set correctly so your shell can find them. 8. After the initial `bk clone' operation to get the source tree, you should run `bk pull' periodically to get the updates. 9. You can examine the change history for the tree with all the diffs by using `bk sccstool'. If you see some funny diffs or code that you have a question about, do not hesitate to send e-mail to . Also, if you think you have a better idea on how to do something, send an email to the same address with a patch. `bk diffs' will produce a patch for you after you have made changes to the source. If you do not have the time to code your idea, just send a description. 10. *BitKeeper* has a nice help utility that you can access via `bk helptool'. Problems Compiling? =================== All *MySQL* programs compile cleanly for us with no warnings on Solaris using `gcc'. On other systems, warnings may occur due to differences in system include files. See *Note MIT-pthreads:: for warnings that may occur when using MIT-pthreads. For other problems, check the list below. The solution to many problems involves reconfiguring. If you do need to reconfigure, take note of the following: * If `configure' is run after it already has been run, it may use information that was gathered during its previous invocation. This information is stored in `config.cache'. When `configure' starts up, it looks for that file and reads its contents if it exists, on the assumption that the information is still correct. That assumption is invalid when you reconfigure. * Each time you run `configure', you must run `make' again to recompile. However, you may want to remove old object files from previous builds first, because they were compiled using different configuration options. To prevent old configuration information or object files from being used, run these commands before rerunning `configure': shell> rm config.cache shell> make clean Alternatively, you can run `make distclean'. The list below describes some of the problems compiling *MySQL* that have been found to occur most often: * If you get errors when compiling `sql_yacc.cc', such as the ones shown below, you have probably run out of memory or swap space: Internal compiler error: program cc1plus got fatal signal 11 or Out of virtual memory or Virtual memory exhausted The problem is that `gcc' requires huge amounts of memory to compile `sql_yacc.cc' with inline functions. Try running `configure' with the `--with-low-memory' option: shell> ./configure --with-low-memory This option causes `-fno-inline' to be added to the compile line if you are using `gcc' and `-O0' if you are using something else. You should try the `--with-low-memory' option even if you have so much memory and swap space that you think you can't possibly have run out. This problem has been observed to occur even on systems with generous hardware configurations, and the `--with-low-memory' option usually fixes it. * By default, `configure' picks `c++' as the compiler name and GNU `c++' links with `-lg++'. If you are using `gcc', that behavior can cause problems during configuration such as this: configure: error: installation or configuration problem: C++ compiler cannot create executables. You might also observe problems during compilation related to `g++', `libg++', or `libstdc++'. One cause of these problems is that you may not have `g++', or you may have `g++' but not `libg++', or `libstdc++'. Take a look at the `config.log' file. It should contain the exact reason why your c++ compiler didn't work! To work around these problems, you can use `gcc' as your C++ compiler. Try setting the environment variable `CXX' to `"gcc -O3"'. For example: shell> CXX="gcc -O3" ./configure This works because `gcc' compiles C++ sources as well as `g++' does, but does not link in `libg++' or `libstdc++' by default. Another way to fix these problems, of course, is to install `g++', `libg++' and `libstdc++'. * If your compile fails with errors, such as any of the following, you must upgrade your version of `make' to GNU `make': making all in mit-pthreads make: Fatal error in reader: Makefile, line 18: Badly formed macro assignment or make: file `Makefile' line 18: Must be a separator (: or pthread.h: No such file or directory Solaris and FreeBSD are known to have troublesome `make' programs. GNU `make' Version 3.75 is known to work. * If you want to define flags to be used by your C or C++ compilers, do so by adding the flags to the `CFLAGS' and `CXXFLAGS' environment variables. You can also specify the compiler names this way using `CC' and `CXX'. For example: shell> CC=gcc shell> CFLAGS=-O3 shell> CXX=gcc shell> CXXFLAGS=-O3 shell> export CC CFLAGS CXX CXXFLAGS See *Note MySQL binaries::, for a list of flag definitions that have been found to be useful on various systems. * If you get an error message like this, you need to upgrade your `gcc' compiler: client/libmysql.c:273: parse error before `__attribute__' `gcc' 2.8.1 is known to work, but we recommend using `gcc' 2.95.2 or `egcs' 1.0.3a instead. * If you get errors such as those shown below when compiling `mysqld', `configure' didn't correctly detect the type of the last argument to `accept()', `getsockname()', or `getpeername()': cxx: Error: mysqld.cc, line 645: In this statement, the referenced type of the pointer value "&length" is "unsigned long", which is not compatible with "int". new_sock = accept(sock, (struct sockaddr *)&cAddr, &length); To fix this, edit the `config.h' file (which is generated by `configure'). Look for these lines: /* Define as the base type of the last arg to accept */ #define SOCKET_SIZE_TYPE XXX Change `XXX' to `size_t' or `int', depending on your operating system. (Note that you will have to do this each time you run `configure', because `configure' regenerates `config.h'.) * The `sql_yacc.cc' file is generated from `sql_yacc.yy'. Normally the build process doesn't need to create `sql_yacc.cc', because *MySQL* comes with an already-generated copy. However, if you do need to re-create it, you might encounter this error: "sql_yacc.yy", line xxx fatal: default action causes potential... This is a sign that your version of `yacc' is deficient. You probably need to install `bison' (the GNU version of `yacc') and use that instead. * If you need to debug `mysqld' or a *MySQL* client, run `configure' with the `--with-debug' option, then recompile and link your clients with the new client library. *Note Debugging client::. MIT-pthreads Notes ================== This section describes some of the issues involved in using MIT-pthreads. Note that on Linux you should NOT use MIT-pthreads but install LinuxThreads! *Note Linux::. If your system does not provide native thread support, you will need to build *MySQL* using the MIT-pthreads package. This includes older FreeBSD systems, SunOS 4.x, Solaris 2.4 and earlier, and some others. *Note Which OS::. * On most systems, you can force MIT-pthreads to be used by running `configure' with the `--with-mit-threads' option: shell> ./configure --with-mit-threads Building in a non-source directory is not supported when using MIT-pthreads, because we want to minimize our changes to this code. * The checks that determine whether or not to use MIT-pthreads occur only during the part of the configuration process that deals with the server code. If you have configured the distribution using `--without-server' to build only the client code, clients will not know whether or not MIT-pthreads is being used and will use Unix socket connections by default. Because Unix sockets do not work under MIT-pthreads, this means you will need to use `-h' or `--host' when you run client programs. * When *MySQL* is compiled using MIT-pthreads, system locking is disabled by default for performance reasons. You can tell the server to use system locking with the `--use-locking' option. * Sometimes the pthread `bind()' command fails to bind to a socket without any error message (at least on Solaris). The result is that all connections to the server fail. For example: shell> mysqladmin version mysqladmin: connect to server at '' failed; error: 'Can't connect to mysql server on localhost (146)' The solution to this is to kill the `mysqld' server and restart it. This has only happened to us when we have forced the server down and done a restart immediately. * With MIT-pthreads, the `sleep()' system call isn't interruptible with `SIGINT' (break). This is only noticeable when you run `mysqladmin --sleep'. You must wait for the `sleep()' call to terminate before the interrupt is served and the process stops. * When linking, you may receive warning messages like these (at least on Solaris); they can be ignored: ld: warning: symbol `_iob' has differing sizes: (file /my/local/pthreads/lib/libpthread.a(findfp.o) value=0x4; file /usr/lib/libc.so value=0x140); /my/local/pthreads/lib/libpthread.a(findfp.o) definition taken ld: warning: symbol `__iob' has differing sizes: (file /my/local/pthreads/lib/libpthread.a(findfp.o) value=0x4; file /usr/lib/libc.so value=0x140); /my/local/pthreads/lib/libpthread.a(findfp.o) definition taken * Some other warnings also can be ignored: implicit declaration of function `int strtoll(...)' implicit declaration of function `int strtoul(...)' * We haven't gotten `readline' to work with MIT-pthreads. (This isn't needed, but may be interesting for someone.) Perl Installation Comments ========================== Installing Perl on Unix ----------------------- Perl support for *MySQL* is provided by means of the `DBI'/`DBD' client interface. *Note Perl::. The Perl `DBD'/`DBI' client code requires Perl Version 5.004 or later. The interface *will not work* if you have an older version of Perl. *MySQL* Perl support also requires that you've installed *MySQL* client programming support. If you installed *MySQL* from RPM files, client programs are in the client RPM, but client programming support is in the developer RPM. Make sure you've installed the latter RPM. As of Version 3.22.8, Perl support is distributed separately from the main *MySQL* distribution. If you want to install Perl support, the files you will need can be obtained from `http://www.mysql.com/Downloads/Contrib/'. The Perl distributions are provided as compressed `tar' archives and have names like `MODULE-VERSION.tar.gz', where `MODULE' is the module name and `VERSION' is the version number. You should get the `Data-Dumper', `DBI', and `Msql-Mysql-modules' distributions and install them in that order. The installation procedure is shown below. The example shown is for the `Data-Dumper' module, but the procedure is the same for all three distributions: 1. Unpack the distribution into the current directory: shell> gunzip < Data-Dumper-VERSION.tar.gz | tar xvf - This command creates a directory named `Data-Dumper-VERSION'. 2. Change into the top-level directory of the unpacked distribution: shell> cd Data-Dumper-VERSION 3. Build the distribution and compile everything: shell> perl Makefile.PL shell> make shell> make test shell> make install The `make test' command is important because it verifies that the module is working. Note that when you run that command during the `Msql-Mysql-modules' installation to exercise the interface code, the *MySQL* server must be running or the test will fail. It is a good idea to rebuild and reinstall the `Msql-Mysql-modules' distribution whenever you install a new release of *MySQL*, particularly if you notice symptoms such as all your `DBI' scripts dumping core after you upgrade *MySQL*. If you don't have the right to install Perl modules in the system directory or if you to install local Perl modules, the following reference may help you: `http://www.iserver.com/support/contrib/perl5/modules.html' Look under the heading `Installing New Modules that Require Locally Installed Modules'. Installing ActiveState Perl on Windows -------------------------------------- To install the *MySQL* `DBD' module with ActiveState Perl on Windows, you should do the following: * Get ActiveState Perl from `http://www.activestate.com/Products/ActivePerl/index.html' and install it. * Open a DOS shell. * If required, set the HTTP_proxy variable. For example, you might try: set HTTP_proxy=my.proxy.com:3128 * Start the PPM program: C:\> c:\perl\bin\ppm.pl * If you have not already done so, install `DBI': ppm> install DBI * If this succeeds, run the following command: install ftp://ftp.de.uu.net/pub/CPAN/authors/id/JWIED/DBD-mysql-1.2212.x86.ppd The above should work at least with ActiveState Perl Version 5.6. If you can't get the above to work, you should instead install the *MyODBC* driver and connect to *MySQL* server through ODBC: use DBI; $dbh= DBI->connect("DBI:ODBC:$dsn","$user","$password") || die "Got error $DBI::errstr when connecting to $dsn\n"; Installing the MySQL Perl Distribution on Windows ------------------------------------------------- The *MySQL* Perl distribution contains `DBI', `DBD:MySQL' and `DBD:ODBC'. * Get the Perl distribution for Windows from `http://www.mysql.com/download.html'. * Unzip the distribution in `C:' so that you get a `C:\PERL' directory. * Add the directory `C:\PERL\BIN' to your path. * Add the directory `C:\PERL\BIN\MSWIN32-x86-thread' or `C:\PERL\BIN\MSWIN32-x86' to your path. * Test that `perl' works by executing `perl -v' in a DOS shell. Problems Using the Perl `DBI'/`DBD' Interface --------------------------------------------- If Perl reports that it can't find the `../mysql/mysql.so' module, then the problem is probably that Perl can't locate the shared library `libmysqlclient.so'. You can fix this by any of the following methods: * Compile the `Msql-Mysql-modules' distribution with `perl Makefile.PL -static -config' rather than `perl Makefile.PL'. * Copy `libmysqlclient.so' to the directory where your other shared libraries are located (probably `/usr/lib' or `/lib'). * On Linux you can add the pathname of the directory where `libmysqlclient.so' is located to the `/etc/ld.so.conf' file. * Add the pathname of the directory where `libmysqlclient.so' is located to the `LD_RUN_PATH' environment variable. If you get the following errors from `DBD-mysql', you are probably using `gcc' (or using an old binary compiled with `gcc'): /usr/bin/perl: can't resolve symbol '__moddi3' /usr/bin/perl: can't resolve symbol '__divdi3' Add `-L/usr/lib/gcc-lib/... -lgcc' to the link command when the `mysql.so' library gets built (check the output from `make' for `mysql.so' when you compile the Perl client). The `-L' option should specify the pathname of the directory where `libgcc.a' is located on your system. Another cause of this problem may be that Perl and *MySQL* aren't both compiled with `gcc'. In this case, you can solve the mismatch by compiling both with `gcc'. If you get the following error from `Msql-Mysql-modules' when you run the tests: t/00base............install_driver(mysql) failed: Can't load '../blib/arch/auto/DBD/mysql/mysql.so' for module DBD::mysql: ../blib/arch/auto/DBD/mysql/mysql.so: undefined symbol: uncompress at /usr/lib/perl5/5.00503/i586-linux/DynaLoader.pm line 169. it means that you need to include the compression library, -lz, to the link line. This can be doing the following change in the file `lib/DBD/mysql/Install.pm': $sysliblist .= " -lm"; to $sysliblist .= " -lm -lz"; After this, you MUST run 'make realclean' and then proceed with the installation from the beginning. If you want to use the Perl module on a system that doesn't support dynamic linking (like SCO) you can generate a static version of Perl that includes `DBI' and `DBD-mysql'. The way this works is that you generate a version of Perl with the `DBI' code linked in and install it on top of your current Perl. Then you use that to build a version of Perl that additionally has the `DBD' code linked in, and install that. On SCO, you must have the following environment variables set: shell> LD_LIBRARY_PATH=/lib:/usr/lib:/usr/local/lib:/usr/progressive/lib or shell> LD_LIBRARY_PATH=/usr/lib:/lib:/usr/local/lib:/usr/ccs/lib:/usr/progressive/lib:/usr/skunk/lib shell> LIBPATH=/usr/lib:/lib:/usr/local/lib:/usr/ccs/lib:/usr/progressive/lib:/usr/skunk/lib shell> MANPATH=scohelp:/usr/man:/usr/local1/man:/usr/local/man:/usr/skunk/man: First, create a Perl that includes a statically linked `DBI' by running these commands in the directory where your `DBI' distribution is located: shell> perl Makefile.PL -static -config shell> make shell> make install shell> make perl Then you must install the new Perl. The output of `make perl' will indicate the exact `make' command you will need to execute to perform the installation. On SCO, this is `make -f Makefile.aperl inst_perl MAP_TARGET=perl'. Next, use the just-created Perl to create another Perl that also includes a statically-linked `DBD::mysql' by running these commands in the directory where your `Msql-Mysql-modules' distribution is located: shell> perl Makefile.PL -static -config shell> make shell> make install shell> make perl Finally, you should install this new Perl. Again, the output of `make perl' indicates the command to use. System-specific Issues ====================== The following sections indicate some of the issues that have been observed to occur on particular systems when installing *MySQL* from a source distribution. Solaris Notes ------------- On Solaris, you may run into trouble even before you get the *MySQL* distribution unpacked! Solaris `tar' can't handle long file names, so you may see an error like this when you unpack *MySQL*: x mysql-3.22.12-beta/bench/Results/ATIS-mysql_odbc-NT_4.0-cmp-db2,informix,ms-sql,mysql,oracle,solid,sybase, 0 bytes, 0 tape blocks tar: directory checksum error In this case, you must use GNU `tar' (`gtar') to unpack the distribution. You can find a precompiled copy for Solaris at `http://www.mysql.com/Downloads/'. Sun native threads work only on Solaris 2.5 and higher. For Version 2.4 and earlier, *MySQL* will automatically use MIT-pthreads. *Note MIT-pthreads::. If you get the following error from configure: checking for restartable system calls... configure: error can not run test programs while cross compiling This means that you have something wrong with your compiler installation! In this case you should upgrade your compiler to a newer version. You may also be able to solve this problem by inserting the following row into the `config.cache' file: ac_cv_sys_restartable_syscalls=${ac_cv_sys_restartable_syscalls='no'} If you are using Solaris on a SPARC, the recommended compiler is `gcc' 2.95.2. You can find this at `http://gcc.gnu.org/'. Note that `egcs' 1.1.1 and `gcc' 2.8.1 don't work reliably on SPARC! The recommended `configure' line when using `gcc' 2.95.2 is: CC=gcc CFLAGS="-O3" \ CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" \ ./configure --prefix=/usr/local/mysql --with-low-memory --enable-assembler If you have a ultra sparc, you can get 4 % more performance by adding "-mcpu=v8 -Wa,-xarch=v8plusa" to CFLAGS and CXXFLAGS. If you have the Sun Workshop (SunPro) 4.2 (or newer) compiler, you can run `configure' like this: CC=cc CFLAGS="-Xa -fast -xO4 -native -xstrconst -mt" \ CXX=CC CXXFLAGS="-noex -xO4 -mt" \ ./configure --prefix=/usr/local/mysql --enable-assembler You may also have to edit the `configure' script to change this line: #if !defined(__STDC__) || __STDC__ != 1 to this: #if !defined(__STDC__) If you turn on `__STDC__' with the `-Xc' option, the Sun compiler can't compile with the Solaris `pthread.h' header file. This is a Sun bug (broken compiler or broken include file). If `mysqld' issues the error message shown below when you run it, you have tried to compile *MySQL* with the Sun compiler without enabling the multi-thread option (`-mt'): libc internal error: _rmutex_unlock: rmutex not held Add `-mt' to `CFLAGS' and `CXXFLAGS' and try again. If you get the following error when compiling *MySQL* with `gcc', it means that your `gcc' is not configured for your version of Solaris: shell> gcc -O3 -g -O2 -DDBUG_OFF -o thr_alarm ... ./thr_alarm.c: In function `signal_hand': ./thr_alarm.c:556: too many arguments to function `sigwait' The proper thing to do in this case is to get the newest version of `gcc' and compile it with your current `gcc' compiler! At least for Solaris 2.5, almost all binary versions of `gcc' have old, unusable include files that will break all programs that use threads (and possibly other programs)! Solaris doesn't provide static versions of all system libraries (`libpthreads' and `libdl'), so you can't compile *MySQL* with `--static'. If you try to do so, you will get the error: ld: fatal: library -ldl: not found If too many processes try to connect very rapidly to `mysqld', you will see this error in the *MySQL* log: Error in accept: Protocol error You might try starting the server with the `--set-variable back_log=50' option as a workaround for this. *Note Command-line options::. If you are linking your own *MySQL* client, you might get the following error when you try to execute it: ld.so.1: ./my: fatal: libmysqlclient.so.#: open failed: No such file or directory The problem can be avoided by one of the following methods: * Link the client with the following flag (instead of `-Lpath'): `-Wl,r/full-path-to-libmysqlclient.so'. * Copy `libmysqclient.so' to `/usr/lib'. * Add the pathname of the directory where `libmysqlclient.so' is located to the `LD_RUN_PATH' environment variable before running your client. When using the `--with-libwrap' configure option, you must also include the libraries that `libwrap.a' needs: --with-libwrap="/opt/NUtcpwrapper-7.6/lib/libwrap.a -lnsl -lsocket If you have problems with configure trying to link with `-lz' and you don't have `zlib' installed, you have two options: * If you want to be able to use the compressed communication protocol, you need to get and install zlib from ftp.gnu.org. * Configure with `--with-named-z-libs=no'. If you are using gcc and have problems with loading `UDF' functions into *MySQL*, try adding `-lgcc' to the link line for the `UDF' function. If you would like *MySQL* to start automatically, you can copy `support-files/mysql.server' to `/etc/init.d' and create a symbolic link to it named `/etc/rc3.d/S99mysql.server'. Solaris 2.7/2.8 Notes --------------------- You can normally use a Solaris 2.6 binary on Solaris 2.7 and 2.8. Most of the Solaris 2.6 issues also apply for Solaris 2.7 and 2.8. Note that *MySQL* Version 3.23.4 and above should be able to autodetect new versions of Solaris and enable workarounds for the following problems! Solaris 2.7 / 2.8 has some bugs in the include files. You may see the following error when you use `gcc': /usr/include/widec.h:42: warning: `getwc' redefined /usr/include/wchar.h:326: warning: this is the location of the previous definition If this occurs, you can do the following to fix the problem: Copy `/usr/include/widec.h' to `.../lib/gcc-lib/os/gcc-version/include' and change line 41 from: #if !defined(lint) && !defined(__lint) to #if !defined(lint) && !defined(__lint) && !defined(getwc) Alternatively, you can edit `/usr/include/widec.h' directly. Either way, after you make the fix, you should remove `config.cache' and run `configure' again! If you get errors like this when you run `make', it's because `configure' didn't detect the `curses.h' file (probably because of the error in `/usr/include/widec.h'): In file included from mysql.cc:50: /usr/include/term.h:1060: syntax error before `,' /usr/include/term.h:1081: syntax error before `;' The solution to this is to do one of the following: * Configure with `CFLAGS=-DHAVE_CURSES_H CXXFLAGS=-DHAVE_CURSES_H ./configure'. * Edit `/usr/include/widec.h' as indicted above and rerun configure. * Remove the `#define HAVE_TERM' line from `config.h' file and run `make' again. If you get a problem that your linker can't find `-lz' when linking your client program, the problem is probably that your `libz.so' file is installed in `/usr/local/lib'. You can fix this by one of the following methods: * Add `/usr/local/lib' to `LD_LIBRARY_PATH'. * Add a link to `libz.so' from `/lib'. * If you are using Solaris 8, you can install the optional zlib from your Solaris 8 CD distribution. * Configure *MySQL* with the `--with-named-z-libs=no' option. Solaris x86 Notes ----------------- If you are using `gcc' or `egcs' on Solaris x86 and you experience problems with core dumps under load, you should use the following `configure' command: CC=gcc CFLAGS="-O3 -fomit-frame-pointer -DHAVE_CURSES_H" \ CXX=gcc \ CXXFLAGS="-O3 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti -DHAVE_CURSES_H" \ ./configure --prefix=/usr/local/mysql This will avoid problems with the `libstdc++' library and with C++ exceptions. If this doesn't help, you should compile a debug version and run it with a trace file or under `gdb'. *Note Using gdb on mysqld::. SunOS 4 Notes ------------- On SunOS 4, MIT-pthreads is needed to compile *MySQL*, which in turn means you will need GNU `make'. Some SunOS 4 systems have problems with dynamic libraries and `libtool'. You can use the following `configure' line to avoid this problem: shell> ./configure --disable-shared --with-mysqld-ldflags=-all-static When compiling `readline', you may get warnings about duplicate defines. These may be ignored. When compiling `mysqld', there will be some `implicit declaration of function' warnings. These may be ignored. Linux Notes (All Linux Versions) -------------------------------- The notes below regarding *glibc* apply only to the situation when you build *MySQL* yourself. If you are running Linux on an x86 machine, in most cases it is much better for you to just use our binary. We link our binaries against the best patched version of *glibc* we can come up with and with the best compiler options, in an attempt to make it suitable for a high-load server. So if you read the text below, and are in doubt about what you should do, try our binary first to see if it meets your needs, and worry about your own build only after you have discovered that our binary is not good enough. In that case, we would appreciate a note about it, so we can build a better binary next time. For a typical user, even for setups with a lot of concurrent connections and/or tables exceeding 2GB limit, our binary in most cases is the best choice. *MySQL* uses LinuxThreads on Linux. If you are using an old Linux version that doesn't have `glibc2', you must install LinuxThreads before trying to compile *MySQL*. You can get LinuxThreads at `http://www.mysql.com/Downloads/Linux'. Note that `glibc' versions before and including Version 2.1.1 have a fatal bug in `pthread_mutex_timedwait' handling, which is used when you do `INSERT DELAYED'. We recommend you to not use `INSERT DELAYED' before upgrading glibc. If you plan to have 1000+ concurrent connections, you will need to make some changes to LinuxThreads, recompile it, and relink *MySQL* against the new `libpthread.a'. Increase `PTHREAD_THREADS_MAX' in `sysdeps/unix/sysv/linux/bits/local_lim.h' to 4096 and decrease `STACK_SIZE' in `linuxthreads/internals.h' to 256 KB. The paths are relative to the root of `glibc' Note that *MySQL* will not be stable with around 600-1000 connections if `STACK_SIZE' is the default of 2 MB. The `STACK_SIZE' constant in LinuxThreads controls the spacing of thread stacks in the address space. It needs to be large enough so that there will be plenty of room for the stack of each individual thread, but small enough to keep the stack of some thread from running into the global `mysqld' data. Unfortunately, the Linux implementation of `mmap()', as we have experimentally discovered, will successfully unmap an already mapped region if you ask it to map out an address already in use, zeroing out the data on the entire page, instead of returning an error. So, the safety of `mysqld' or any other threaded application depends on the "gentleman" behavior of the code that creates threads. The user must take measures to make sure the number of running threads at any time is sufficiently low for thread stacks to stay away from the global heap. With `mysqld', you should enforce this "gentleman" behavior by setting a reasonable value for the `max_connections' variable. If you build *MySQL* yourself and do not what to mess with patching LinuxThreads, you should set `max_connections' to a value no higher than 500. It should be even less if you have a large key buffer, large heap tables, or some other things that make *mysqld* allocate a lot of memory or if you are running a 2.2 kernel with a 2GB patch. If you are using our binary or RPM version 3.23.25 or later, you can safely set `max_connections' at 1500, assuming no large key buffer or heap tables with lots of data. The more you reduce `STACK_SIZE' in LinuxThreads the more threads you can safely create. We recommend the values between 128K and 256K. If you use a lot of concurrent connections, you may suffer from a "feature" in the 2.2 kernel that penalizes a process for forking or cloning a child in an attempt to prevent a fork bomb attack. This will cause *MySQL* not to scale well as you increase the number of concurrent clients. On single CPU systems, we have seen this manifested in a very slow thread creation, which means it may take a long time to connect to *MySQL* (as long as 1 minute), and it may take just as long to shut it down. On multiple CPU systems, we have observed a gradual drop in query speed as the number of clients increases. In the process of trying to find a solution, we have received a kernel patch from one of our users, who claimed it made a lot of difference for his site. The patch is available here (`http://www.mysql.com/Downloads/Patches/linux-fork.patch'). We have now done rather extensive testing of this patch on both development and production systems. It has significantly improved `MySQL' performance without causing any problems and we now recommend it to our users who are still running high-load servers on 2.2 kernels. This issue has been fixed in the 2.4 kernel, so if you are not satisfied with the current performance of your system, rather than patching your 2.2 kernel, it might be easier to just upgrade to 2.4, which will also give you a nice SMP boost in addition to fixing this fairness bug. We have tested *MySQL* on the 2.4 kernel on a 2 CPU machine and found *MySQL* scales MUCH better - there was virtually no slowdown on query throughput all the way up to 1000 clients, and *MySQL* scaling factor ( computed as the ratio of maximum throughput to the throughput with one client) was 180%. We have observed similar results on a 4-CPU system - virtually no slowdown as the number of clients was increased up to 1000, and 300% scaling factor. So for a high-load SMP server we would definitely recommend the 2.4 kernel at this point. We have discovered that it is essential to run `mysqld' process with the highest possible priority on the 2.4 kernel to achieve maximum performance. This can be done by adding `renice -20 $$' command to `safe_mysqld'. In our testing on a 4-CPU machine, increasing the priority gave 60% increase in throughput with 400 clients. We are currently also trying to collect more info on how well `MySQL' performs on 2.4 kernel on 4-way and 8-way systems. If you have access such a system and have done some benchmarks, please send a mail to with the results - we will include them in the manual. There is another issue that greatly hurts *MySQL* performance, especially on SMP systems. The implementation of mutex in LinuxThreads in *glibc-2.1* is very bad for programs with many threads that only hold the mutex for a short time. On an SMP system, ironic as it is, if you link *MySQL* against unmodified *LinuxThreads*, removing processors from the machine improves *MySQL* performance in many cases. We have made a patch available for *glibc 2.1.3*, linuxthreads-2.1-patch (http://www.mysql.com/Downloads/Linux/linuxthreads-2.1-patch) to correct this behavior. With *glibc-2.2.2* *MySQL* version 3.23.36 will use the adaptive mutex, which is much better than even the patched one in *glibc-2.1.3*. Be warned, however, that under some conditions, the current mutex code in *glibc-2.2.2* overspins, which hurts *MySQL* performance. The chance of this condition can be reduced by renicing `mysqld' process to the highest priority. We have also been able to correct the overspin behavior with a patch, available here (http://www.mysql.com/Downloads/Linux/linuxthreads-2.2.2.patch). It combines the correction of overspin, maximum number of threads, and stack spacing all in one. You will need to apply it in the `linuxthreads' directory with `patch -p0 cp support-files/mysql.server /etc/init.d/mysql.server shell> /usr/sbin/update-rc.d mysql.server defaults 99 `mysql.server' can be found in the `share/mysql' directory under the *MySQL* installation directory or in the `support-files' directory of the *MySQL* source tree. If `mysqld' always core dumps when it starts up, the problem may be that you have an old `/lib/libc.a'. Try renaming it, then remove `sql/mysqld' and do a new `make install' and try again. This problem has been reported on some Slackware installations. RedHat Version 5.0 also has a similar problem with some new `glibc' versions. *Note Linux-RedHat50::. If you get the following error when linking `mysqld', it means that your `libg++.a' is not installed correctly: /usr/lib/libc.a(putc.o): In function `_IO_putc': putc.o(.text+0x0): multiple definition of `_IO_putc' You can avoid using `libg++.a' by running `configure' like this: shell> CXX=gcc ./configure RedHat Version 5.0 Notes ........................ If you have any problems with *MySQL* on RedHat, you should start by upgrading `glibc' to the newest possible version! If you install all the official RedHat patches (including `glibc-2.0.7-19' and `glibc-devel-2.0.7-19'), both the binary and source distributions of *MySQL* should work without any trouble! The updates are needed because there is a bug in `glibc' 2.0.5 in how `pthread_key_create' variables are freed. With `glibc' 2.0.5, you must use a statically linked *MySQL* binary distribution. If you want to compile from source, you must install the corrected version of LinuxThreads from `http://www.mysql.com/Downloads/Linux' or upgrade your `glibc'. If you have an incorrect version of `glibc' or LinuxThreads, the symptom is that `mysqld' crashes after each connection. For example, `mysqladmin version' will crash `mysqld' when it finishes! Another symptom of incorrect libraries is that `mysqld' crashes at once when it starts. On some Linux systems, this can be fixed by configuring like this: shell> ./configure --with-mysqld-ldflags=-all-static On Redhat Version 5.0, the easy way out is to install the `glibc' 2.0.7-19 RPM and run `configure' *without* the `--with-mysqld-ldflags=-all-static' option. For the source distribution of `glibc' 2.0.7, a patch that is easy to apply and is tested with *MySQL* may be found at: `http://www.mysql.com/Downloads/Linux/glibc-2.0.7-total-patch.tar.gz' If you experience crashes like these when you build *MySQL*, you can always download the newest binary version of *MySQL*. This is statically-linked to avoid library conflicts and should work on all Linux systems! *MySQL* comes with an internal debugger that can generate trace files with a lot of information that can be used to find and solve a wide range of different problems. *Note Debugging server::. RedHat Version 5.1 notes ........................ The `glibc' of RedHat Version 5.1 (`glibc' 2.0.7-13) has a memory leak, so to get a stable *MySQL* version, you must upgrade `glibc', to 2.0.7-19, downgrade `glibc' or use a binary version of `mysqld'. If you don't do this, you will encounter memory problems (out of memory, etc.). The most common error in this case is: Can't create a new thread (errno 11). If you are not out of available memory, you can consult the manual for any possible OS dependent bug After you have upgraded to `glibc' 2.0.7-19, you can configure *MySQL* with dynamic linking (the default), but you *cannot* run `configure' with the `--with-mysqld-ldflags=-all-static' option until you have installed `glibc' 2.0.7-19 from source! You can check which version of `glibc' you have with `rpm -q glibc'. Another reason for the above error is if you try to use more threads than your Linux kernel is configured for. In this case you should raise the limits in `include/linux/tasks.h' and recompile your kernel! Linux-SPARC Notes ................. In some implementations, `readdir_r()' is broken. The symptom is that `SHOW DATABASES' always returns an empty set. This can be fixed by removing `HAVE_READDIR_R' from `config.h' after configuring and before compiling. Some problems will require patching your Linux installation. The patch can be found at `http://www.mysql.com/Downloads/patches/Linux-sparc-2.0.30.diff'. This patch is against the Linux distribution `sparclinux-2.0.30.tar.gz' that is available at `vger.rutgers.edu' (a version of Linux that was never merged with the official 2.0.30). You must also install LinuxThreads Version 0.6 or newer. Linux-Alpha Notes ................. *MySQL* Version 3.23.12 is the first *MySQL* version that is tested on Linux-Alpha. If you plan to use *MySQL* on Linux-Alpha, you should ensure that you have this version or newer. We have tested *MySQL* on Alpha with our benchmarks and test suite, and it appears to work nicely. The main thing we haven't yet had time to test is how things works with many concurrent users. When we compiled the standard *MySQL* binary we are using SuSE 6.4, kernel 2.2.13-SMP, Compaq C compiler (V6.2-504) and Compaq C++ compiler (V6.3-005) on a Comaq DS20 machine with an Alpha EV6 processor. You can find the above compilers at `http://www.support.compaq.com/alpha-tools'). By using these compilers, instead of gcc, we get about 9-14 % better performance with *MySQL*. Note that the configure line optimized the binary for the current CPU; This means you can only use our binary if you have an Alpha EV6 processor. We also compile statically to avoid library problems. CC=ccc CFLAGS="-fast" CXX=cxx CXXFLAGS="-fast -noexceptions -nortti" ./configure --prefix=/usr/local/mysql --disable-shared --with-extra-charsets=complex --enable-thread-safe-client --with-mysqld-ldflags=-non_shared --with-client-ldflags=-non_shared If you want to use egcs the following configure line worked for us: CFLAGS="-O3 -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O3 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --disable-shared Some known problems when running *MySQL* on Linux-Alpha: * Debugging threaded applications like *MySQL* will not work with `gdb 4.18'. You should download and use gdb 5.0 instead! * If you try linking `mysqld' statically when using `gcc', the resulting image will core dump at start. In other words, *DON'T* use `--with-mysqld-ldflags=-all-static' with `gcc'. MkLinux Notes ............. *MySQL* should work on MkLinux with the newest `glibc' package (tested with `glibc' 2.0.7). Qube2 Linux Notes ................. To get *MySQL* to work on Qube2, (Linux Mips), you need the newest `glibc' libraries (`glibc-2.0.7-29C2' is known to work). You must also use the `egcs' C++ compiler (`egcs-1.0.2-9', `gcc 2.95.2' or newer). Linux IA64 Notes ................ To get *MySQL* to compile on Linux Ia64, we had to do the following (we assume that this will be easier when next gcc version for ia64 is released). Using `gcc-2.9-final': CFLAGS="-O2" CXX=gcc CXXFLAGS="-O2 -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --disable-shared --with-extra-charsets=complex After `make' you will get an error that `sql/opt_range.cc' will not compile (internal compiler error). To fix this, go to the sql directory and type `make' again. Copy the compile line, but change -O2 to -O0. The file should now compile. Now you can do: cd .. make make_install and *mysqld* should be ready to run. Alpha-DEC-UNIX Notes (Tru64) ---------------------------- If you are using egcs 1.1.2 on Digital Unix, you should upgrade to gcc 2.95.2, as egcs on DEC has some serious bugs! When compiling threaded programs under Digital Unix, the documentation recommends using the `-pthread' option for `cc' and `cxx' and the libraries `-lmach -lexc' (in addition to `-lpthread'). You should run `configure' something like this: CC="cc -pthread" CXX="cxx -pthread -O" \ ./configure --with-named-thread-libs="-lpthread -lmach -lexc -lc" When compiling `mysqld', you may see a couple of warnings like this: mysqld.cc: In function void handle_connections()': mysqld.cc:626: passing long unsigned int *' as argument 3 of accept(int,sockadddr *, int *)' You can safely ignore these warnings. They occur because `configure' can detect only errors, not warnings. If you start the server directly from the command line, you may have problems with it dying when you log out. (When you log out, your outstanding processes receive a `SIGHUP' signal.) If so, try starting the server like this: shell> nohup mysqld [options] & `nohup' causes the command following it to ignore any `SIGHUP' signal sent from the terminal. Alternatively, start the server by running `safe_mysqld', which invokes `mysqld' using `nohup' for you. *Note `safe_mysqld': safe_mysqld. If you get a problem when compiling mysys/get_opt.c, just remove the line #define _NO_PROTO from the start of that file! If you are using Compac's CC compiler, the following configure line should work: CC="cc -pthread" CFLAGS="-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host" CXX="cxx -pthread" CXXFLAGS="-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host" export CC CFLAGS CXX CXXFLAGS ./configure \ --prefix=/usr/local/mysql \ --with-low-memory \ --enable-large-files \ --enable-shared=yes \ --with-named-thread-libs="-lpthread -lmach -lexc -lc" gnumake If you get a problem with libtool, when compiling with shared libraries as above, when linking `mysql', you should be able to get around this by issuing: cd mysql /bin/sh ../libtool --mode=link cxx -pthread -O3 -DDBUG_OFF \ -O4 -ansi_alias -ansi_args -fast -inline speed \ -speculate all \ -arch host -DUNDEF_HAVE_GETHOSTBYNAME_R \ -o mysql mysql.o readline.o sql_string.o completion_hash.o \ ../readline/libreadline.a -lcurses \ ../libmysql/.libs/libmysqlclient.so -lm cd .. gnumake gnumake install scripts/mysql_install_db Alpha-DEC-OSF1 Notes -------------------- If you have problems compiling and have DEC `CC' and `gcc' installed, try running `configure' like this: CC=cc CFLAGS=-O CXX=gcc CXXFLAGS=-O3 \ ./configure --prefix=/usr/local/mysql If you get problems with the `c_asm.h' file, you can create and use a 'dummy' `c_asm.h' file with: touch include/c_asm.h CC=gcc CFLAGS=-I./include \ CXX=gcc CXXFLAGS=-O3 \ ./configure --prefix=/usr/local/mysql Note that the following problems with the `ld' program can be fixed by downloading the latest DEC (Compaq) patch kit from: `http://ftp.support.compaq.com/public/unix/'. On OSF1 V4.0D and compiler "DEC C V5.6-071 on Digital Unix V4.0 (Rev. 878)" the compiler had some strange behavior (undefined `asm' symbols). `/bin/ld' also appears to be broken (problems with `_exit undefined' errors occuring while linking `mysqld'). On this system, we have managed to compile *MySQL* with the following `configure' line, after replacing `/bin/ld' with the version from OSF 4.0C: CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql With the Digital compiler "C++ V6.1-029", the following should work: CC=cc -pthread CFLAGS=-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host CXX=cxx -pthread CXXFLAGS=-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host -noexceptions -nortti export CC CFLAGS CXX CXXFLAGS ./configure --prefix=/usr/mysql/mysql --with-mysqld-ldflags=-all-static --disable-shared --with-named-thread-libs="-lmach -lexc -lc" In some versions of OSF1, the `alloca()' function is broken. Fix this by removing the line in `config.h' that defines `'HAVE_ALLOCA''. The `alloca()' function also may have an incorrect prototype in `/usr/include/alloca.h'. This warning resulting from this can be ignored. `configure' will use the following thread libraries automatically: `--with-named-thread-libs="-lpthread -lmach -lexc -lc"'. When using `gcc', you can also try running `configure' like this: shell> CFLAGS=-D_PTHREAD_USE_D4 CXX=gcc CXXFLAGS=-O3 ./configure .... If you have problems with signals (*MySQL* dies unexpectedly under high load), you may have found an OS bug with threads and signals. In this case you can tell *MySQL* not to use signals by configuring with: shell> CFLAGS=-DDONT_USE_THR_ALARM \ CXXFLAGS=-DDONT_USE_THR_ALARM \ ./configure ... This doesn't affect the performance of *MySQL*, but has the side effect that you can't kill clients that are "sleeping" on a connection with `mysqladmin kill' or `mysqladmin shutdown'. Instead, the client will die when it issues its next command. With `gcc' 2.95.2, you will probably run into the following compile error: sql_acl.cc:1456: Internal compiler error in `scan_region', at except.c:2566 Please submit a full bug report. To fix this you should change to the `sql' directory and do a "cut and paste" of the last `gcc' line, but change `-O3' to `-O0' (or add `-O0' immediately after `gcc' if you don't have any `-O' option on your compile line.) After this is done you can just change back to the top-level directly and run `make' again. SGI-Irix Notes -------------- If you are using Irix Version 6.5.3 or newer `mysqld' will only be able to create threads if you run it as a user with `CAP_SCHED_MGT' privileges (like `root') or give the `mysqld' server this privilege with the following shell command: shell> chcap "CAP_SCHED_MGT+epi" /opt/mysql/libexec/mysqld You may have to undefine some things in `config.h' after running `configure' and before compiling. In some Irix implementations, the `alloca()' function is broken. If the `mysqld' server dies on some `SELECT' statements, remove the lines from `config.h' that define `HAVE_ALLOC' and `HAVE_ALLOCA_H'. If `mysqladmin create' doesn't work, remove the line from `config.h' that defines `HAVE_READDIR_R'. You may have to remove the `HAVE_TERM_H' line as well. SGI recommends that you install all of the patches on this page as a set: http://support.sgi.com/surfzone/patches/patchset/6.2_indigo.rps.html At the very minimum, you should install the latest kernel rollup, the latest `rld' rollup, and the latest `libc' rollup. You definitely need all the POSIX patches on this page, for pthreads support: `http://support.sgi.com/surfzone/patches/patchset/6.2_posix.rps.html' If you get the something like the following error when compiling `mysql.cc': "/usr/include/curses.h", line 82: error(1084): invalid combination of type Type the following in the top-level directory of your *MySQL* source tree: shell> extra/replace bool curses_bool < /usr/include/curses.h > include/curses.h shell> make There have also been reports of scheduling problems. If only one thread is running, things go slow. Avoid this by starting another client. This may lead to a 2-to-10-fold increase in execution speed thereafter for the other thread. This is a poorly understood problem with Irix threads; you may have to improvise to find solutions until this can be fixed. If you are compiling with `gcc', you can use the following `configure' command: CC=gcc CXX=gcc CXXFLAGS=-O3 \ ./configure --prefix=/usr/local/mysql --with-thread-safe-client --with-named-thread-libs=-lpthread FreeBSD Notes ------------- FreeBSD 3.x is recommended for running *MySQL* since the thread package is much more integrated. The easiest and therefor the preferred way to install is to use the mysql-server and mysql-client ports available on `http://www.freebsd.org'. Using these gives you: * A working *MySQL* with all optimizations known to work on your version of FreeBSD enabled. * Automatic configuration and build. * Startup scripts installed in /usr/local/etc/rc.d. * Ability to see which files that are installed with pkg_info -L. And to remove them all with pkg_delete if you no longer want *MySQL* on that machine. It is recommended you use MIT-pthreads on FreeBSD 2.x and native threads on Versions 3 and up. It is possible to run with native threads on some late 2.2.x versions but you may encounter problems shutting down `mysqld'. The *MYSQL* Makefiles require GNU make (`gmake') to work. If you want to compile *MYSQL* you need to install GNU make first. Be sure to have your name resolver setup correct. Otherwise you may experience resolver delays or failures when connecting to `mysqld'. Make sure that the `localhost' entry in the `/etc/hosts' file is correct (otherwise you will have problems connecting to the database). The `/etc/hosts' file should start with a line: 127.0.0.1 localhost localhost.your.domain If you notice that `configure' will use MIT-pthreads, you should read the MIT-pthreads notes. *Note MIT-pthreads::. If you get an error from `make install' that it can't find `/usr/include/pthreads', `configure' didn't detect that you need MIT-pthreads. This is fixed by executing these commands: shell> rm config.cache shell> ./configure --with-mit-threads FreeBSD is also known to have a very low default file handle limit. *Note Not enough file handles::. Uncomment the ulimit -n section in safe_mysqld or raise the limits for the `mysqld' user in /etc/login.conf (and rebuild it with cap_mkdb /etc/login.conf). Also be sure you set the appropriate class for this user in the password file if you are not using the default (use: chpass mysqld-user-name). *Note `safe_mysqld': safe_mysqld. If you get problems with the current date in *MySQL*, setting the `TZ' variable will probably help. *Note Environment variables::. To get a secure and stable system you should only use FreeBSD kernels that are marked `-STABLE'. NetBSD notes ------------ To compile on NetBSD you need GNU `make'. Otherwise the compile will crash when `make' tries to run `lint' on C++ files. OpenBSD Notes ------------- OpenBSD 2.5 Notes ................. On OpenBSD Version 2.5, you can compile *MySQL* with native threads with the following options: CFLAGS=-pthread CXXFLAGS=-pthread ./configure --with-mit-threads=no OpenBSD 2.8 Notes ................. Our users have reported that OpenBSD 2.8 has a threading bug which causes problems with *MySQL*. The OpenBSD Developers have fixed the problem, but as of January 25th, 2001, it's only available in the "-current" branch. The symptoms of this threading bug are: slow response, high load, high CPU usage, and crashes. BSD/OS Notes ------------ BSD/OS Version 2.x Notes ........................ If you get the following error when compiling *MySQL*, your `ulimit' value for virtual memory is too low: item_func.h: In method `Item_func_ge::Item_func_ge(const Item_func_ge &)': item_func.h:28: virtual memory exhausted make[2]: *** [item_func.o] Error 1 Try using `ulimit -v 80000' and run `make' again. If this doesn't work and you are using `bash', try switching to `csh' or `sh'; some BSDI users have reported problems with `bash' and `ulimit'. If you are using `gcc', you may also use have to use the `--with-low-memory' flag for `configure' to be able to compile `sql_yacc.cc'. If you get problems with the current date in *MySQL*, setting the `TZ' variable will probably help. *Note Environment variables::. BSD/OS Version 3.x Notes ........................ Upgrade to BSD/OS Version 3.1. If that is not possible, install BSDIpatch M300-038. Use the following command when configuring *MySQL*: shell> env CXX=shlicc++ CC=shlicc2 \ ./configure \ --prefix=/usr/local/mysql \ --localstatedir=/var/mysql \ --without-perl \ --with-unix-socket-path=/var/mysql/mysql.sock The following is also known to work: shell> env CC=gcc CXX=gcc CXXFLAGS=-O3 \ ./configure \ --prefix=/usr/local/mysql \ --with-unix-socket-path=/var/mysql/mysql.sock You can change the directory locations if you wish, or just use the defaults by not specifying any locations. If you have problems with performance under heavy load, try using the `--skip-thread-priority' option to `mysqld'! This will run all threads with the same priority; on BSDI Version 3.1, this gives better performance (at least until BSDI fixes their thread scheduler). If you get the error `virtual memory exhausted' while compiling, you should try using `ulimit -v 80000' and run `make' again. If this doesn't work and you are using `bash', try switching to `csh' or `sh'; some BSDI users have reported problems with `bash' and `ulimit'. BSD/OS Version 4.x Notes ........................ BSDI Version 4.x has some thread-related bugs. If you want to use *MySQL* on this, you should install all thread-related patches. At least M400-023 should be installed. On some BSDI Version 4.x systems, you may get problems with shared libraries. The symptom is that you can't execute any client programs, for example, `mysqladmin'. In this case you need to reconfigure not to use shared libraries with the `--disable-shared' option to configure. Some customers have had problems on BSDI 4.0.1 that the `mysqld' binary after a while can't open tables. This is because some library/system related bug causes `mysqld' to change current directory without asking for this! The fix is to either upgrade to 3.23.34 or after running `configure' remove the line `#define HAVE_REALPATH' from `config.h' before running make. Note that the above means that you can't symbolic link a database directories to another database directory or symbolic link a table to another database on BSDI! (Making a symbolic link to another disk is ok). SCO Notes --------- The current port is tested only on a "sco3.2v5.0.4" and "sco3.2v5.0.5" system. There has also been a lot of progress on a port to "sco 3.2v4.2". For the moment the recommended compiler on OpenServer is gcc 2.95.2. With this you should be able to compile *MySQL* with just: CC=gcc CXX=gcc ./configure ... (options) 1. For OpenServer 5.0.X you need to use GDS in Skunkware 95 (95q4c). This is necessary because GNU `gcc' 2.7.2 in Skunkware 97 does not have GNU `as'. You can also use `egcs' 1.1.2 or newer `http://www.egcs.com/'. If you are using `egcs' 1.1.2 you have to execute the following command: shell> cp -p /usr/include/pthread/stdtypes.h /usr/local/lib/gcc-lib/i386-pc-sco3.2v5.0.5/egcs-2.91.66/include/pthread/ 2. You need the port of GCC 2.5.x for this product and the Development system. They are required on this version of SCO Unix. You cannot just use the GCC Dev system. 3. You should get the FSU Pthreads package and install it first. This can be found at `http://www.cs.wustl.edu/~schmidt/ACE_wrappers/FSU-threads.tar.gz'. You can also get a precompiled package from `http://www.mysql.com/Downloads/SCO/FSU-threads-3.5c.tar.gz'. 4. FSU Pthreads can be compiled with SCO Unix 4.2 with tcpip. Or OpenServer 3.0 or Open Desktop 3.0 (OS 3.0 ODT 3.0), with the SCO Development System installed using a good port of GCC 2.5.x ODT or OS 3.0 you will need a good port of GCC 2.5.x There are a lot of problems without a good port. The port for this product requires the SCO Unix Development system. Without it, you are missing the libraries and the linker that is needed. 5. To build FSU Pthreads on your system, do the following: a. Run `./configure' in the `threads/src' directory and select the SCO OpenServer option. This command copies `Makefile.SCO5' to `Makefile'. b. Run `make'. c. To install in the default `/usr/include' directory, login as root, then `cd' to the `thread/src' directory, and run `make install'. 6. Remember to use GNU `make' when making *MySQL*. 7. If you don't start `safe_mysqld' as root, you probably will get only the default 110 open files per process. `mysqld' will write a note about this in the log file. 8. With SCO 3.2V5.0.5, you should use FSU Pthreads version 3.5c or newer. You should also use gcc 2.95.2 or newer! The following `configure' command should work: shell> ./configure --prefix=/usr/local/mysql --disable-shared 9. With SCO 3.2V4.2, you should use FSU Pthreads version 3.5c or newer. The following `configure' command should work: shell> CFLAGS="-D_XOPEN_XPG4" CXX=gcc CXXFLAGS="-D_XOPEN_XPG4" \ ./configure \ --prefix=/usr/local/mysql \ --with-named-thread-libs="-lgthreads -lsocket -lgen -lgthreads" \ --with-named-curses-libs="-lcurses" You may get some problems with some include files. In this case, you can find new SCO-specific include files at `http://www.mysql.com/Downloads/SCO/SCO-3.2v4.2-includes.tar.gz'. You should unpack this file in the `include' directory of your *MySQL* source tree. SCO development notes: * *MySQL* should automatically detect FSU Pthreads and link `mysqld' with `-lgthreads -lsocket -lgthreads'. * The SCO development libraries are re-entrant in FSU Pthreads. SCO claims that its libraries' functions are re-entrant, so they must be reentrant with FSU Pthreads. FSU Pthreads on OpenServer tries to use the SCO scheme to make re-entrant libraries. * FSU Pthreads (at least the version at `http://www.mysql.com/') comes linked with GNU `malloc'. If you encounter problems with memory usage, make sure that `gmalloc.o' is included in `libgthreads.a' and `libgthreads.so'. * In FSU Pthreads, the following system calls are pthreads-aware: `read()', `write()', `getmsg()', `connect()', `accept()', `select()', and `wait()'. If you want to install DBI on SCO, you have to edit the `Makefile' in DBI-xxx and each subdirectory. Note that the following assumes gcc 2.95.2 or newer: OLD: NEW: CC = cc CC = gcc CCCDLFLAGS = -KPIC -W1,-Bexport CCCDLFLAGS = -fpic CCDLFLAGS = -wl,-Bexport CCDLFLAGS = LD = ld LD = gcc -G -fpic LDDLFLAGS = -G -L/usr/local/lib LDDLFLAGS = -L/usr/local/lib LDFLAGS = -belf -L/usr/local/lib LDFLAGS = -L/usr/local/lib LD = ld LD = gcc -G -fpic OPTIMISE = -Od OPTIMISE = -O1 OLD: CCCFLAGS = -belf -dy -w0 -U M_XENIX -DPERL_SCO5 -I/usr/local/include NEW: CCFLAGS = -U M_XENIX -DPERL_SCO5 -I/usr/local/include This is because the Perl dynaloader will not load the `DBI' modules if they were compiled with `icc' or `cc'. Perl works best when compiled with `cc'. SCO Unixware Version 7.0 Notes ------------------------------ You must use a version of *MySQL* at least as recent as Version 3.22.13 because that version fixes some portability problems under Unixware. We have been able to compile *MySQL* with the following `configure' command on Unixware Version 7.0.1: CC=cc CXX=CC ./configure --prefix=/usr/local/mysql If you want to use `gcc', you must use `gcc' 2.95.2 or newer. IBM-AIX notes ------------- Automatic detection of `xlC' is missing from Autoconf, so a `configure' command something like this is needed when compiling *MySQL* (This example uses the IBM compiler): export CC="xlc_r -ma -O3 -qstrict -qoptimize=3 -qmaxmem=8192 " export CXX="xlC_r -ma -O3 -qstrict -qoptimize=3 -qmaxmem=8192" export CFLAGS="-I /usr/local/include" export LDLFAGS="-L /usr/local/lib" export CPPFLAGS=$CFLAGS export CXXFLAGS=$CFLAGS ./configure --prefix=/usr/local \ --localstatedir=/var/mysql \ --sysconfdir=/etc/mysql \ --sbindir='/usr/local/bin' \ --libexecdir='/usr/local/bin' \ --enable-thread-safe-client \ --enable-large-files Above are the options used to compile the *MySQL* distribution that can be found at `http://www-frec.bull.com/'. If you change the `-O3' to `-O2' in the above configure line, you must also remove the `-qstrict' option (this is a limitation in the IBM C compiler). If you are using `gcc' or `egcs' to compile *MySQL*, you *MUST* use the `-fno-exceptions' flag, as the exception handling in `gcc'/`egcs' is not thread safe! (This is tested with `egcs' 1.1.). There are also some known problems with IBM's assembler, which may cause it to generate bad code when used with gcc. We recommend the following `configure' line with `egcs' and `gcc 2.95' on AIX: CC="gcc -pipe -mcpu=power -Wa,-many" \ CXX="gcc -pipe -mcpu=power -Wa,-many" \ CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti" \ ./configure --prefix=/usr/local/mysql --with-low-memory The `-Wa,-many' is necessary for the compile to be successful. IBM is aware of this problem but is in to hurry to fix it because of the workaround available. We don't know if the `-fno-exceptions' is required with `gcc 2.95', but as *MySQL* doesn't use exceptions and the above option generates faster code, we recommend that you should always use this option with `egcs / gcc'. If you get a problem with assembler code try changing the -mcpu=xxx to match your cpu. Typically power2, power, or powerpc may need to be used, alternatively you might need to use 604 or 604e. I'm not positive but I would think using "power" would likely be safe most of the time, even on a power2 machine. If you don't know what your cpu is then do a "uname -m", this will give you back a string that looks like "000514676700", with a format of xxyyyyyymmss where xx and ss are always 0's, yyyyyy is a unique system id and mm is the id of the CPU Planar. A chart of these values can be found at `http://www.rs6000.ibm.com/doc_link/en_US/a_doc_lib/cmds/aixcmds5/uname.htm'. This will give you a machine type and a machine model you can use to determine what type of cpu you have. If you have problems with signals (*MySQL* dies unexpectedly under high load) you may have found an OS bug with threads and signals. In this case you can tell *MySQL* not to use signals by configuring with: shell> CFLAGS=-DDONT_USE_THR_ALARM CXX=gcc \ CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti -DDONT_USE_THR_ALARM" \ ./configure --prefix=/usr/local/mysql --with-debug --with-low-memory This doesn't affect the performance of *MySQL*, but has the side effect that you can't kill clients that are "sleeping" on a connection with `mysqladmin kill' or `mysqladmin shutdown'. Instead, the client will die when it issues its next command. On some versions of AIX, linking with `libbind.a' makes `getservbyname' core dump. This is an AIX bug and should be reported to IBM. For AIX 4.2.1 and gcc you have to do the following changes. After configuring, edit `config.h' and `include/my_config.h' and change the line that says #define HAVE_SNPRINTF 1 to #undef HAVE_SNPRINTF And finally, in `mysqld.cc' you need to add a prototype for initgoups. #ifdef _AIX41 extern "C" int initgroups(const char *,int); #endif HP-UX Version 10.20 Notes ------------------------- There are a couple of small problems when compiling *MySQL* on HP-UX. We recommend that you use `gcc' instead of the HP-UX native compiler, because `gcc' produces better code! We recommend using gcc 2.95 on HP-UX. Don't use high optimization flags (like -O6) as this may not be safe on HP-UX. Note that MIT-pthreads can't be compiled with the HP-UX compiler because it can't compile `.S' (assembler) files. The following configure line should work: CFLAGS="-DHPUX -I/opt/dce/include" CXXFLAGS="-DHPUX -I/opt/dce/include -felide-constructors -fno-exceptions -fno-rtti" CXX=gcc ./configure --with-pthread --with-named-thread-libs='-ldce' --prefix=/usr/local/mysql --disable-shared If you are compiling `gcc' 2.95 yourself, you should NOT link it with the DCE libraries (`libdce.a' or `libcma.a') if you want to compile *MySQL* with MIT-pthreads. If you mix the DCE and MIT-pthreads packages you will get a `mysqld' to which you cannot connect. Remove the DCE libraries while you compile `gcc' 2.95! HP-UX Version 11.x Notes ------------------------ For HP-UX Version 11.x we recommend *MySQL* Version 3.23.15 or later. Because of some critical bugs in the standard HP-UX libraries, you should install the following patches before trying to run *MySQL* on HP-UX 11.0: PHKL_22840 Streams cumulative PHNE_22397 ARPA cumulative This will solve a problem that one gets `EWOULDBLOCK' from `recv()' and `EBADF' from `accept()' in threaded applications. If you are using `gcc' 2.95.1 on an unpatched HP-UX 11.x system, you will get the error: In file included from /usr/include/unistd.h:11, from ../include/global.h:125, from mysql_priv.h:15, from item.cc:19: /usr/include/sys/unistd.h:184: declaration of C function ... /usr/include/sys/pthread.h:440: previous declaration ... In file included from item.h:306, from mysql_priv.h:158, from item.cc:19: The problem is that HP-UX doesn't define `pthreads_atfork()' consistently. It has conflicting prototypes in `/usr/include/sys/unistd.h':184 and `/usr/include/sys/pthread.h':440 (details below). One solution is to copy `/usr/include/sys/unistd.h' into `mysql/include' and edit `unistd.h' and change it to match the definition in `pthread.h'. Here's the diff: 183,184c183,184 < extern int pthread_atfork(void (*prepare)(), void (*parent)(), < void (*child)()); --- > extern int pthread_atfork(void (*prepare)(void), void (*parent)(void), > void (*child)(void)); After this, the following configure line should work: CFLAGS="-fomit-frame-pointer -O3 -fpic" CXX=gcc CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti -O3" ./configure --prefix=/usr/local/mysql --disable-shared Here is some information that a HP-UX Version 11.x user sent us about compiling *MySQL* with HP-UX:x compiler: Environment: proper compilers. setenv CC cc setenv CXX aCC flags setenv CFLAGS -D_REENTRANT setenv CXXFLAGS -D_REENTRANT setenv CPPFLAGS -D_REENTRANT % aCC -V aCC: HP ANSI C++ B3910B X.03.14.06 % cc -V /tmp/empty.c cpp.ansi: HP92453-01 A.11.02.00 HP C Preprocessor (ANSI) ccom: HP92453-01 A.11.01.00 HP C Compiler cc: "/tmp/empty.c", line 1: warning 501: Empty source file. configuration: ./configure --with-pthread \ --prefix=/source-control/mysql \ --with-named-thread-libs=-lpthread \ --with-low-memory added '#define _CTYPE_INCLUDED' to include/m_ctype.h. This symbol is the one defined in HP's /usr/include/ctype.h: /* Don't include std ctype.h when this is included */ #define _CTYPE_H #define __CTYPE_INCLUDED #define _CTYPE_INCLUDED #define _CTYPE_USING /* Don't put names in global namespace. */ * I had to use the compile-time flag `-D_REENTRANT' to get the compiler to recognize the prototype for `localtime_r'. Alternatively I could have supplied the prototype for `localtime_r'. But I wanted to catch other bugs without needing to run into them. I wasn't sure where I needed it, so I added it to all flags. * The optimization flags used by *MySQL* (-O3) are not recognized by HP's compilers. I did not change the flags. If you get the following error from `configure' checking for cc option to accept ANSI C... no configure: error: MySQL requires a ANSI C compiler (and a C++ compiler). Try gcc. See the Installation chapter in the Reference Manual. Check that you don't have the path to the K&R compiler before the path to the HP-UX C and C++ compiler. Mac OS X Notes -------------- Mac OS X Public beta .................... *MySQL* should work without any problems on Mac OS X Public Beta (Darwin). You don't need the pthread patches for this OS! Mac OS X Server ............... Before trying to configure *MySQL* on Mac OS X server you must first install the pthread package from `http://www.prnet.de/RegEx/mysql.html'. Our binary for Mac OS X is compiled on Rhapsody 5.5 with the following configure line: CC=gcc CFLAGS="-O2 -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O2 -fomit-frame-pointer" ./configure --prefix=/usr/local/mysql "--with-comment=Official MySQL binary" --with-extra-charsets=complex --disable-shared You might want to also add aliases to your shell's resource file to access `mysql' and `mysqladmin' from the command line: alias mysql '/usr/local/mysql/bin/mysql' alias mysqladmin '/usr/local/mysql/bin/mysqladmin' BeOS Notes ---------- We are really interested in getting *MySQL* to work on BeOS, but unfortunately we don't have any person who knows BeOS or has time to do a port. We are interested in finding someone to do a port, and we will help them with any technical questions they may have while doing the port. We have previously talked with some BeOS developers that have said that *MySQL* is 80% ported to BeOS, but we haven't heard from them in a while. Windows Notes ============= This section describes installation and use of *MySQL* on Windows. This information is also provided in the `README' file that comes with the *MySQL* Windows distribution. Installing MySQL on Windows --------------------------- The following instructions apply to precompiled binary distributions. If you download a source distribution, you will have to compile and install it yourself. If you don't have a copy of the *MySQL* distribution, you should first download one from `http://www.mysql.com/downloads/mysql-3.23.html'. If you plan to connect to *MySQL* from some other program, you will probably also need the *MyODBC* driver. You can find this at the *MyODBC* download page (`http://www.mysql.com/downloads/api-myodbc.html'). To install either distribution, unzip it in some empty directory and run the `Setup.exe' program. By default, *MySQL*-Windows is configured to be installed in `C:\mysql'. If you want to install *MySQL* elsewhere, install it in `C:\mysql' first, then move the installation to where you want it. If you do move *MySQL*, you must indicate where everything is located by supplying a `--basedir' option when you start the server. For example, if you have moved the *MySQL* distribution to `D:\programs\mysql', you must start `mysqld' like this: C:\> D:\programs\mysql\bin\mysqld --basedir D:\programs\mysql Use `mysqld --help' to display all the options that `mysqld' understands! With all newer *MySQL* versions, you can also create a `C:\my.cnf' file that holds any default options for the *MySQL* server. Copy the file `\mysql\my-xxxxx.cnf' to `C:\my.cnf' and edit it to suit your setup. Note that you should specify all paths with `/' instead of `\'. If you use `\', you need to specify it twice, because `\' is the escape character in *MySQL*. *Note Option files::. Starting with *MySQL* 3.23.38, the Windows distribution includes both the normal and the *MySQL-Max* binaries. The main benefit of using the normal `mysqld.exe' binary is that it's a little faster and uses less resources. Here is a list of the different *MySQL* servers you can use: `mysqld' Compiled with full debugging and automatic memory allocation checking, symbolic links, BDB and InnoDB tables. `mysqld-opt' Optimized binary with no support for transactional tables. `mysqld-nt' Optimized binary for NT with support for named pipes. You can run this version on Win98, but in this case no named pipes are created and you must have TCP/IP installed. `mysqld-max' Optimized binary with support for symbolic links, BDB and InnoDB tables. `mysqld-max-nt' Like `mysqld-max', but compiled with support for named pipes. All of the above binaries are optimized for the Pentium Pro processor but should work on any Intel processor >= i386. NOTE: If you want to use InnoDB tables, there are certain startup options that must be specified in your `my.ini' file! *Note InnoDB start::. Starting MySQL on Windows 95 or Windows 98 ------------------------------------------ *MySQL* uses TCP/IP to connect a client to a server. (This will allow any machine on your network to connect to your *MySQL* server.) Because of this, you must install TCP/IP on your machine before starting *MySQL*. You can find TCP/IP on your Windows CD-ROM. Note that if you are using an old Win95 release (for example OSR2), it's likely that you have an old Winsock package! *MySQL* requires Winsock 2! You can get the newest Winsock from `http://www.microsoft.com/'. Win98 has the new Winsock 2 library, so the above doesn't apply for Win98. To start the `mysqld' server, you should start an MS-DOS window and type: C:\> C:\mysql\bin\mysqld This will start `mysqld' in the background without a window. You can kill the *MySQL* server by executing: C:\> C:\mysql\bin\mysqladmin -u root shutdown Note that Win95 and Win98 don't support creation of named pipes. On Win95 and Win98, you can only use named pipes to connect to a remote *MySQL* server running on a Windows NT server host. (The *MySQL* server must also support named pipes, of course. For example, using `mysqld-opt' under NT will not allow named pipe connections. You should use either `mysqld-nt' or `mysqld-max-nt'.) If `mysqld' doesn't start, please check whether or not the `\mysql\data\mysql.err' file contains any reason for this. You can also try to start the server with `mysqld --standalone'; In this case, you may get some useful information on the screen that may help solve the problem. The last option is to start `mysqld' with `--standalone --debug'. In this case `mysqld' will write a log file `C:\mysqld.trace' that should contain the reason why `mysqld' doesn't start. *Note Making trace files::. Starting MySQL on Windows NT or Windows 2000 -------------------------------------------- The Win95/Win98 section also applies to *MySQL* on NT/Win2000, with the following differences: To get *MySQL* to work with TCP/IP on NT, you must install service pack 3 (or newer)! Note that everything in the following that applies for NT also applies for Win2000! For NT/Win2000, the server name is `mysqld-nt'. Normally you should install *MySQL* as a service on NT/Win2000: C:\> C:\mysql\bin\mysqld-nt --install or C:\> C:\mysql\bin\mysqld-max-nt --install (You can also use `mysqld' binaries that don't end with `-nt.exe' on NT, but those cannot be started as a service or use named pipes.) You can start and stop the *MySQL* service with these commands: C:\> NET START mysql C:\> NET STOP mysql Note that in this case you can't use any other options for `mysqld-nt'! You can also run `mysqld-nt' as a stand-alone program on NT if you need to start `mysqld-nt' with any options! If you start `mysqld-nt' without options on NT, `mysqld-nt' tries to start itself as a service with the default service options. If you have stopped `mysqld-nt', you have to start it with `NET START mysql'. The service is installed with the name `MySQL'. Once installed, it must be started using the Services Control Manager (SCM) Utility found in the Control Panel, or by using the `NET START MySQL' command. If any options are desired, they must be specified as "Startup parameters" in the SCM utility before you start the *MySQL* service. Once running, `mysqld-nt' can be stopped using `mysqladmin', or from the SCM utility or by using the command `NET STOP MySQL'. If you use SCM to stop `mysqld-nt', there is a strange message from SCM about `mysqld shutdown normally'. When run as a service, `mysqld-nt' has no access to a console and so no messages can be seen. On NT you can get the following service error messages: Permission Denied Means that it cannot find `mysqld-nt.exe'. Cannot Register Means that the path is incorrect. Failed to install Means that the service is already installed or service. that the Service Control Manager is in bad state. If you have problems installing `mysqld-nt' as a service, try starting it with the full path: C:\> C:\mysql\bin\mysqld-nt --install If this doesn't work, you can get `mysqld-nt' to start properly by fixing the path in the registry! If you don't want to start `mysqld-nt' as a service, you can start it as follows: C:\> C:\mysql\bin\mysqld-nt --standalone or C:\> C:\mysql\bin\mysqld --standalone --debug The last version gives you a debug trace in `C:\mysqld.trace'. *Note Making trace files::. Running MySQL on Windows ------------------------ *MySQL* supports TCP/IP on all Windows platforms and named pipes on NT. The default is to use named pipes for local connections on NT and TCP/IP for all other cases if the client has TCP/IP installed. The host name specifies which protocol is used: *Host name* *Protocol* NULL (none) On NT, try named pipes first; if that doesn't work, use TCP/IP. On Win95/Win98, TCP/IP is used. . Named pipes localhost TCP/IP to current host hostname TCP/IP You can force a *MySQL* client to use named pipes by specifying the `--pipe' option or by specifying `.' as the host name. Use the `--socket' option to specify the name of the pipe. You can test whether or not *MySQL* is working by executing the following commands: C:\> C:\mysql\bin\mysqlshow C:\> C:\mysql\bin\mysqlshow -u root mysql C:\> C:\mysql\bin\mysqladmin version status proc C:\> C:\mysql\bin\mysql test If `mysqld' is slow to answer to connections on Win95/Win98, there is probably a problem with your DNS. In this case, start `mysqld' with `--skip-name-resolve' and use only `localhost' and IP numbers in the *MySQL* grant tables. You can also avoid DNS when connecting to a `mysqld-nt' *MySQL* server running on NT by using the `--pipe' argument to specify use of named pipes. This works for most *MySQL* clients. There are two versions of the *MySQL* command-line tool: `mysql' Compiled on native Windows, which offers very limited text editing capabilities. `mysqlc' Compiled with the Cygnus GNU compiler and libraries, which offers `readline' editing. If you want to use `mysqlc.exe', you must copy `C:\mysql\lib\cygwinb19.dll' to your Windows system directory (`\windows\system' or similar place). The default privileges on Windows give all local users full privileges to all databases without specifying a password. To make *MySQL* more secure, you should set a password for all users and remove the row in the `mysql.user' table that has `Host='localhost'' and `User='''. You should also add a password for the `root' user. The following example starts by removing the anonymous user that can be used by anyone to access the `test' database, then sets a `root' user password: C:\> C:\mysql\bin\mysql mysql mysql> DELETE FROM user WHERE Host='localhost' AND User=''; mysql> QUIT C:\> C:\mysql\bin\mysqladmin reload C:\> C:\mysql\bin\mysqladmin -u root password your_password After you've set the password, if you want to take down the `mysqld' server, you can do so using this command: C:\> mysqladmin --user=root --password=your_password shutdown If you are using the old shareware version of *MySQL* Version 3.21 under Windows, the above command will fail with an error: `parse error near 'SET OPTION password''. The fix is in to upgrade to the current *MySQL* version, which is freely available. With the current *MySQL* versions you can easily add new users and change privileges with `GRANT' and `REVOKE' commands. *Note GRANT::. Connecting to a Remote MySQL from Windows with SSH -------------------------------------------------- Here is a note about how to connect to get a secure connection to remote *MySQL* server with SSH (by David Carlson ): * Install an SSH client on your Windows machine. As a user, the best non-free one I've found is from `SecureCRT' from `http://www.vandyke.com/'. Another option is `f-secure' from `http://www.f-secure.com/'. You can also find some free ones on *Google* at `http://directory.google.com/Top/Computers/Security/Products_and_Tools/Cryptography/SSH/Clients/Windows/'. * Start your Windows SSH client. Set `Host_Name = yourmysqlserver_URL_or_IP'. Set `userid=your_userid' to log in to your server (probably not the same as your *MySQL* login/password. * Set up port forwarding. Either do a remote forward (Set `local_port: 3306', `remote_host: yourmysqlservername_or_ip', `remote_port: 3306' ) or a local forward (Set `port: 3306', `host: localhost', `remote port: 3306'). * Save everything, otherwise you'll have to redo it the next time. * Log in to your server with SSH session you just created. * On your Windows machine, start some ODBC application (such as Access). * Create a new file in Windows and link to *MySQL* using the ODBC driver the same way you normally do, EXCEPT type in `localhost' for the *MySQL* host server -- not `yourmysqlservername'. You should now have an ODBC connection to *MySQL*, encrypted using SSH. Splitting Data Across Different Disks on Windows ------------------------------------------------ Beginning with *MySQL* Version 3.23.16, the `mysqld-max' and `mysql-max-nt' servers in the *MySQL* distribution are compiled with the `-DUSE_SYMDIR' option. This allows you to put a database on different disk by adding a symbolic link to it (in a manner similar to the way that symbolic links work on Unix). On Windows, you make a symbolic link to a database by creating a file that contains the path to the destination directory and saving this in the `mysql_data' directory under the filename `database.sym'. Note that the symbolic link will be used only if the directory `mysql_data_dir\database' doesn't exist. For example, if the *MySQL* data directory is `C:\mysql\data' and you want to have database `foo' located at `D:\data\foo', you should create the file `C:\mysql\data\foo.sym' that contains the text `D:\data\foo\'. After that, all tables created in the database `foo' will be created in `D:\data\foo'. Note that because of the speed penalty you get when opening every table, we have not enabled this by default even if you have compiled *MySQL* with support for this. To enable symlinks you should put in your `my.cnf' or `my.ini' file the following entry: [mysqld] use-symbolic-links In *MySQL* 4.0 we will enable symlinks by default. Then you should instead use the `skip-symlink' option if you want to disable this. Compiling MySQL Clients on Windows ---------------------------------- In your source files, you should include `windows.h' before you include `mysql.h': #if defined(_WIN32) || defined(_WIN64) #include #endif #include You can either link your code with the dynamic `libmysql.lib' library, which is just a wrapper to load in `libmysql.dll' on demand, or link with the static `mysqlclient.lib' library. Note that as the mysqlclient libraries are compiled as threaded libraries, you should also compile your code to be multi-threaded! MySQL-Windows Compared to Unix MySQL ------------------------------------ *MySQL*-Windows has by now proven itself to be very stable. This version of *MySQL* has the same features as the corresponding Unix version with the following exceptions: *Win95 and threads* Win95 leaks about 200 bytes of main memory for each thread creation. Each connection in *MySQL* creates a new thread, so you shouldn't run `mysqld' for an extended time on Win95 if your server handles many connections! WinNT and Win98 don't suffer from this bug. *Concurrent reads* *MySQL* depends on the `pread()' and `pwrite()' calls to be able to mix `INSERT' and `SELECT'. Currently we use mutexes to emulate `pread()'/`pwrite()'. We will, in the long run, replace the file level interface with a virtual interface so that we can use the `readfile()'/`writefile()' interface on NT to get more speed. The current implementation limits the number of open files *MySQL* can use to 1024, which means that you will not be able to run as many concurrent threads on NT as on Unix. *Blocking read* *MySQL* uses a blocking read for each connection. This means that: * A connection will not be disconnected automatically after 8 hours, as happens with the Unix version of *MySQL*. * If a connection hangs, it's impossible to break it without killing *MySQL*. * `mysqladmin kill' will not work on a sleeping connection. * `mysqladmin shutdown' can't abort as long as there are sleeping connections. We plan to fix this problem when our Windows developers have figured out a nice workaround. *UDF functions* For the moment, *MySQL*-Windows does not support user-definable functions. *`DROP DATABASE'* You can't drop a database that is in use by some thread. *Killing *MySQL* from the task manager* You can't kill *MySQL* from the task manager or with the shutdown utility in Win95. You must take it down with `mysqladmin shutdown'. *Case-insensitive names* Filenames are case insensitive on Windows, so database and table names are also case insensitive in *MySQL* for Windows. The only restriction is that database and table names must be specified using the same case throughout a given statement. *Note Name case sensitivity::. *The `\' directory character* Pathname components in Win95 are separated by the `\' character, which is also the escape character in *MySQL*. If you are using `LOAD DATA INFILE' or `SELECT ... INTO OUTFILE', you must double the `\' character: mysql> LOAD DATA INFILE "C:\\tmp\\skr.txt" INTO TABLE skr; mysql> SELECT * INTO OUTFILE 'C:\\tmp\\skr.txt' FROM skr; Alternatively, use Unix style filenames with `/' characters: mysql> LOAD DATA INFILE "C:/tmp/skr.txt" INTO TABLE skr; mysql> SELECT * INTO OUTFILE 'C:/tmp/skr.txt' FROM skr; *`Can't open named pipe' error* If you use a *MySQL* 3.22 version on NT with the newest mysql-clients you will get the following error: error 2017: can't open named pipe to host: . pipe... This is because the release version of *MySQL* uses named pipes on NT by default. You can avoid this error by using the `--host=localhost' option to the new *MySQL* clients or create an option file `C:\my.cnf' that contains the following information: [client] host = localhost *`Access denied for user' error* If you get the error `Access denied for user: 'some-user@unknown' to database 'mysql'' when accessing a *MySQL* server on the same machine, this means that *MySQL* can't resolve your host name properly. To fix this, you should create a file `\windows\hosts' with the following information: 127.0.0.1 localhost *`ALTER TABLE'* While you are executing an `ALTER TABLE' statement, the table is locked from usage by other threads. This has to do with the fact that on Windows, you can't delete a file that is in use by another threads. (In the future, we may find some way to work around this problem.) *`DROP TABLE' on a table that is in use by a `MERGE' table will not work* The `MERGE' handler does its table mapping hidden from *MySQL*. Because Windows doesn't allow you to drop files that are open, you first must flush all `MERGE' tables (with `FLUSH TABLES') or drop the `MERGE' table before dropping the table. We will fix this at the same time we introduce `VIEW's. Here are some open issues for anyone who might want to help us with the Windows release: * Make a single-user `MYSQL.DLL' server. This should include everything in a standard *MySQL* server, except thread creation. This will make *MySQL* much easier to use in applications that don't need a true client/server and don't need to access the server from other hosts. * Add some nice start and shutdown icons to the *MySQL* installation. * Create a tool to manage registry entries for the *MySQL* startup options. The registry entry reading is already coded into `mysqld.cc', but it should be recoded to be more parameter oriented. The tool should also be able to update the `C:\my.cnf' option file if the user prefers to use that instead of the registry. * When registering `mysqld' as a service with `--install' (on NT) it would be nice if you could also add default options on the command line. For the moment, the workaround is to list the parameters in the `C:\my.cnf' file instead. * When you suspend a laptop running Win95, the `mysqld' daemon doesn't accept new connections when the laptop is resumed. We don't know if this is a problem with Win95, TCP/IP, or *MySQL*. * It would be real nice to be able to kill `mysqld' from the task manager. For the moment, you must use `mysqladmin shutdown'. * Port `readline' to Windows for use in the `mysql' command line tool. * GUI versions of the standard *MySQL* clients (`mysql', `mysqlshow', `mysqladmin', and `mysqldump') would be nice. * It would be nice if the socket read and write functions in `net.c' were interruptible. This would make it possible to kill open threads with `mysqladmin kill' on Windows. * `mysqld' always starts in the "C" locale and not in the default locale. We would like to have `mysqld' use the current locale for the sort order. * Implement UDF functions with `.DLL's. * Add macros to use the faster thread-safe increment/decrement methods provided by Windows. Other Windows-specific issues are described in the `README' file that comes with the *MySQL*-Windows distribution. OS/2 Notes ========== *MySQL* uses quite a few open files. Because of this, you should add something like the following to your `CONFIG.SYS' file: SET EMXOPT=-c -n -h1024 If you don't do this, you will probably run into the following error: File 'xxxx' not found (Errcode: 24) When using *MySQL* with OS/2 Warp 3, FixPack 29 or above is required. With OS/2 Warp 4, FixPack 4 or above is required. This is a requirement of the Pthreads library. *MySQL* must be installed in a partition that supports long filenames such as HPFS, FAT32, etc. The `INSTALL.CMD' script must be run from OS/2's own `CMD.EXE' and may not work with replacement shells such as `4OS2.EXE'. The `scripts/mysql-install-db' script has been renamed. It is now called `install.cmd' and is a REXX script, which will set up the default *MySQL* security settings and create the WorkPlace Shell icons for *MySQL*. Dynamic module support is compiled in but not fully tested. Dynamic modules should be compiled using the Pthreads run-time library. gcc -Zdll -Zmt -Zcrtdll=pthrdrtl -I../include -I../regex -I.. \ -o example udf_example.cc -L../lib -lmysqlclient udf_example.def mv example.dll example.udf *Note:* Due to limitations in OS/2, UDF module name stems must not exceed 8 characters. Modules are stored in the `/mysql2/udf' directory; the `safe-mysqld.cmd' script will put this directory in the `BEGINLIBPATH' environment variable. When using UDF modules, specified extensions are ignored -- it is assumed to be `.udf'. For example, in Unix, the shared module might be named `example.so' and you would load a function from it like this: mysql> CREATE FUNCTION metaphon RETURNS STRING SONAME "example.so"; Is OS/2, the module would be named `example.udf', but you would not specify the module extension: mysql> CREATE FUNCTION metaphon RETURNS STRING SONAME "example"; MySQL Binaries ============== As a service, we at *MySQL AB* provide a set of binary distributions of *MySQL* that are compiled at our site or at sites where customers kindly have given us access to their machines. These distributions are generated with `scripts/make_binary_distribution' and are configured with the following compilers and options: SunOS 4.1.4 2 sun4c with `gcc' 2.7.2.1 `CC=gcc CXX=gcc CXXFLAGS="-O3 -felide-constructors" ./configure --prefix=/usr/local/mysql --disable-shared --with-extra-charsets=complex --enable-assembler' SunOS 5.5.1 sun4u with `egcs' 1.0.3a `CC=gcc CFLAGS="-O3" CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex' SunOS 5.6 sun4u with `egcs' 2.90.27 `CC=gcc CFLAGS="-O3" CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex' SunOS 5.6 i86pc with `gcc' 2.8.1 `CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex' Linux 2.0.33 i386 with `pgcc' 2.90.29 (`egcs' 1.0.3a) `CFLAGS="-O3 -mpentium -mstack-align-double" CXX=gcc CXXFLAGS="-O3 -mpentium -mstack-align-double -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --with-extra-charsets=complex' Linux 2.2.x with x686 with `gcc' 2.95.2 `CFLAGS="-O3 -mpentiumpro" CXX=gcc CXXFLAGS="-O3 -mpentiumpro -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --disable-shared --with-extra-charset=complex' SCO 3.2v5.0.4 i386 with `gcc' 2.7-95q4 `CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex' AIX 2 4 with `gcc' 2.7.2.2 `CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex' OSF1 V4.0 564 alpha with `gcc' 2.8.1 `CC=gcc CFLAGS=-O CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex' Irix 6.3 IP32 with `gcc' 2.8.0 `CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex' BSDI BSD/OS 3.1 i386 with `gcc' 2.7.2.1 `CC=gcc CXX=gcc CXXFLAGS=-O ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex' BSDI BSD/OS 2.1 i386 with `gcc' 2.7.2 `CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex' Anyone who has more optimal options for any of the configurations listed above can always mail them to the developer's mailing list at . RPM distributions prior to *MySQL* Version 3.22 are user-contributed. Beginning with Version 3.22, the RPMs are generated by us at *MySQL AB*. If you want to compile a debug version of *MySQL*, you should add `--with-debug' or `--with-debug=full' to the above configure lines and remove any `-fomit-frame-pointer' options. Post-installation Setup and Testing =================================== Once you've installed *MySQL* (from either a binary or source distribution), you need to initialize the grant tables, start the server, and make sure that the server works okay. You may also wish to arrange for the server to be started and stopped automatically when your system starts up and shuts down. Normally you install the grant tables and start the server like this for installation from a source distribution: shell> ./scripts/mysql_install_db shell> cd mysql_installation_directory shell> ./bin/safe_mysqld --user=mysql & For a binary distribution (not RPM or pkg packages), do this: shell> cd mysql_installation_directory shell> ./bin/mysql_install_db shell> ./bin/safe_mysqld --user=mysql & This creates the `mysql' database which will hold all database privileges, the `test' database which you can use to test *MySQL* and also privilege entries for the user that run `mysql_install_db' and a `root' user (without any passwords). This also starts the `mysqld' server. `mysql_install_db' will not overwrite any old privilege tables, so it should be safe to run in any circumstances. If you don't want to have the `test' database you can remove it with `mysqladmin -u root drop test'. Testing is most easily done from the top-level directory of the *MySQL* distribution. For a binary distribution, this is your installation directory (typically something like `/usr/local/mysql'). For a source distribution, this is the main directory of your *MySQL* source tree. In the commands shown below in this section and in the following subsections, `BINDIR' is the path to the location in which programs like `mysqladmin' and `safe_mysqld' are installed. For a binary distribution, this is the `bin' directory within the distribution. For a source distribution, `BINDIR' is probably `/usr/local/bin', unless you specified an installation directory other than `/usr/local' when you ran `configure'. `EXECDIR' is the location in which the `mysqld' server is installed. For a binary distribution, this is the same as `BINDIR'. For a source distribution, `EXECDIR' is probably `/usr/local/libexec'. Testing is described in detail below: 1. If necessary, start the `mysqld' server and set up the initial *MySQL* grant tables containing the privileges that determine how users are allowed to connect to the server. This is normally done with the `mysql_install_db' script: shell> scripts/mysql_install_db Typically, `mysql_install_db' needs to be run only the first time you install *MySQL*. Therefore, if you are upgrading an existing installation, you can skip this step. (However, `mysql_install_db' is quite safe to use and will not update any tables that already exist, so if you are unsure of what to do, you can always run `mysql_install_db'.) `mysql_install_db' creates six tables (`user', `db', `host', `tables_priv', `columns_priv', and `func') in the `mysql' database. A description of the initial privileges is given in *Note Default privileges::. Briefly, these privileges allow the *MySQL* `root' user to do anything, and allow anybody to create or use databases with a name of `'test'' or starting with `'test_''. If you don't set up the grant tables, the following error will appear in the log file when you start the server: mysqld: Can't find file: 'host.frm' The above may also happen with a binary *MySQL* distribution if you don't start *MySQL* by executing exactly `./bin/safe_mysqld'! *Note `safe_mysqld': safe_mysqld. You might need to run `mysql_install_db' as `root'. However, if you prefer, you can run the *MySQL* server as an unprivileged (non-`root') user, provided that user can read and write files in the database directory. Instructions for running *MySQL* as an unprivileged user are given in *Note Changing *MySQL* user: Changing MySQL user. If you have problems with `mysql_install_db', see *Note `mysql_install_db': mysql_install_db. There are some alternatives to running the `mysql_install_db' script as it is provided in the *MySQL* distribution: * You may want to edit `mysql_install_db' before running it, to change the initial privileges that are installed into the grant tables. This is useful if you want to install *MySQL* on a lot of machines with the same privileges. In this case you probably should need only to add a few extra `INSERT' statements to the `mysql.user' and `mysql.db' tables! * If you want to change things in the grant tables after installing them, you can run `mysql_install_db', then use `mysql -u root mysql' to connect to the grant tables as the *MySQL* `root' user and issue SQL statements to modify the grant tables directly. * It is possible to re-create the grant tables completely after they have already been created. You might want to do this if you've already installed the tables but then want to re-create them after editing `mysql_install_db'. For more information about these alternatives, see *Note Default privileges::. 2. Start the *MySQL* server like this: shell> cd mysql_installation_directory shell> bin/safe_mysqld & If you have problems starting the server, see *Note Starting server::. 3. Use `mysqladmin' to verify that the server is running. The following commands provide a simple test to check that the server is up and responding to connections: shell> BINDIR/mysqladmin version shell> BINDIR/mysqladmin variables The output from `mysqladmin version' varies slightly depending on your platform and version of *MySQL*, but should be similar to that shown below: shell> BINDIR/mysqladmin version mysqladmin Ver 8.14 Distrib 3.23.32, for linux on i586 Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB This software comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to modify and redistribute it under the GPL license Server version 3.23.32-debug Protocol version 10 Connection Localhost via Unix socket TCP port 3306 UNIX socket /tmp/mysql.sock Uptime: 16 sec Threads: 1 Questions: 9 Slow queries: 0 Opens: 7 Flush tables: 2 Open tables: 0 Queries per second avg: 0.000 Memory in use: 132K Max memory used: 16773K To get a feeling for what else you can do with `BINDIR/mysqladmin', invoke it with the `--help' option. 4. Verify that you can shut down the server: shell> BINDIR/mysqladmin -u root shutdown 5. Verify that you can restart the server. Do this using `safe_mysqld' or by invoking `mysqld' directly. For example: shell> BINDIR/safe_mysqld --log & If `safe_mysqld' fails, try running it from the *MySQL* installation directory (if you are not already there). If that doesn't work, see *Note Starting server::. 6. Run some simple tests to verify that the server is working. The output should be similar to what is shown below: shell> BINDIR/mysqlshow +-----------+ | Databases | +-----------+ | mysql | +-----------+ shell> BINDIR/mysqlshow mysql Database: mysql +--------------+ | Tables | +--------------+ | columns_priv | | db | | func | | host | | tables_priv | | user | +--------------+ shell> BINDIR/mysql -e "select host,db,user from db" mysql +------+--------+------+ | host | db | user | +------+--------+------+ | % | test | | | % | test_% | | +------+--------+------+ There is also a benchmark suite in the `sql-bench' directory (under the *MySQL* installation directory) that you can use to compare how *MySQL* performs on different platforms. The `sql-bench/Results' directory contains the results from many runs against different databases and platforms. To run all tests, execute these commands: shell> cd sql-bench shell> run-all-tests If you don't have the `sql-bench' directory, you are probably using an RPM for a binary distribution. (Source distribution RPMs include the benchmark directory.) In this case, you must first install the benchmark suite before you can use it. Beginning with *MySQL* Version 3.22, there are benchmark RPM files named `mysql-bench-VERSION-i386.rpm' that contain benchmark code and data. If you have a source distribution, you can also run the tests in the `tests' subdirectory. For example, to run `auto_increment.tst', do this: shell> BINDIR/mysql -vvf test < ./tests/auto_increment.tst The expected results are shown in the `./tests/auto_increment.res' file. Problems Running `mysql_install_db' ----------------------------------- The purpose of the `mysql_install_db' script is to generate new *MySQL* privilege tables. It will not affect any other data! It will also not do anything if you already have *MySQL* privilege tables installed! If you want to re-create your privilege tables, you should take down the `mysqld' server, if it's running, and then do something like: mv mysql-data-directory/mysql mysql-data-directory/mysql-old mysql_install_db This section lists problems you might encounter when you run `mysql_install_db': *`mysql_install_db' doesn't install the grant tables* You may find that `mysql_install_db' fails to install the grant tables and terminates after displaying the following messages: starting mysqld daemon with databases from XXXXXX mysql daemon ended In this case, you should examine the log file very carefully! The log should be located in the directory `XXXXXX' named by the error message, and should indicate why `mysqld' didn't start. If you don't understand what happened, include the log when you post a bug report using `mysqlbug'! *Note Bug reports::. *There is already a `mysqld' daemon running* In this case, you probably don't have to run `mysql_install_db' at all. You have to run `mysql_install_db' only once, when you install *MySQL* the first time. *Installing a second `mysqld' daemon doesn't work when one daemon is running* This can happen when you already have an existing *MySQL* installation, but want to put a new installation in a different place (for example, for testing, or perhaps you simply want to run two installations at the same time). Generally the problem that occurs when you try to run the second server is that it tries to use the same socket and port as the old one. In this case you will get the error message: `Can't start server: Bind on TCP/IP port: Address already in use' or `Can't start server : Bind on unix socket...'. *Note Installing many servers::. *You don't have write access to `/tmp'* If you don't have write access to create a socket file at the default place (in `/tmp') or permission to create temporary files in `/tmp,' you will get an error when running `mysql_install_db' or when starting or using `mysqld'. You can specify a different socket and temporary directory as follows: shell> TMPDIR=/some_tmp_dir/ shell> MYSQL_UNIX_PORT=/some_tmp_dir/mysqld.sock shell> export TMPDIR MYSQL_UNIX_PORT `some_tmp_dir' should be the path to some directory for which you have write permission. *Note Environment variables::. After this you should be able to run `mysql_install_db' and start the server with these commands: shell> scripts/mysql_install_db shell> BINDIR/safe_mysqld & *`mysqld' crashes immediately* If you are running RedHat Version 5.0 with a version of `glibc' older than 2.0.7-5, you should make sure you have installed all `glibc' patches! There is a lot of information about this in the *MySQL* mail archives. Links to the mail archives are available online at `http://www.mysql.com/documentation/'. Also, see *Note Linux::. You can also start `mysqld' manually using the `--skip-grant-tables' option and add the privilege information yourself using `mysql': shell> BINDIR/safe_mysqld --skip-grant-tables & shell> BINDIR/mysql -u root mysql From `mysql', manually execute the SQL commands in `mysql_install_db'. Make sure you run `mysqladmin flush-privileges' or `mysqladmin reload' afterward to tell the server to reload the grant tables. Problems Starting the MySQL Server ---------------------------------- If you are going to use tables that support transactions (BDB, InnoDB or Gemini), you should first create a my.cnf file and set startup options for the table types you plan to use. *Note Table types::. Generally, you start the `mysqld' server in one of three ways: * By invoking `mysql.server'. This script is used primarily at system startup and shutdown, and is described more fully in *Note Automatic start::. * By invoking `safe_mysqld', which tries to determine the proper options for `mysqld' and then runs it with those options. *Note `safe_mysqld': safe_mysqld. * On NT you should install `mysqld' as a service as follows: bin\mysqld-nt --install # Install MySQL as a service You can now start/stop `mysqld' as follows: NET START mysql NET STOP mysql Note that in this case you can't use any other options for `mysqld'! You can remove the service as follows: bin\mysqld-nt --remove # remove MySQL as a service * By invoking `mysqld' directly. When the `mysqld' daemon starts up, it changes directory to the data directory. This is where it expects to write log files and the pid (process ID) file, and where it expects to find databases. The data directory location is hardwired in when the distribution is compiled. However, if `mysqld' expects to find the data directory somewhere other than where it really is on your system, it will not work properly. If you have problems with incorrect paths, you can find out what options `mysqld' allows and what the default path settings are by invoking `mysqld' with the `--help' option. You can override the defaults by specifying the correct pathnames as command-line arguments to `mysqld'. (These options can be used with `safe_mysqld' as well.) Normally you should need to tell `mysqld' only the base directory under which *MySQL* is installed. You can do this with the `--basedir' option. You can also use `--help' to check the effect of changing path options (note that `--help' _must_ be the final option of the `mysqld' command). For example: shell> EXECDIR/mysqld --basedir=/usr/local --help Once you determine the path settings you want, start the server without the `--help' option. Whichever method you use to start the server, if it fails to start up correctly, check the log file to see if you can find out why. Log files are located in the data directory (typically `/usr/local/mysql/data' for a binary distribution, `/usr/local/var' for a source distribution, `\mysql\data\mysql.err' on Windows.) Look in the data directory for files with names of the form `host_name.err' and `host_name.log' where `host_name' is the name of your server host. Then check the last few lines of these files: shell> tail host_name.err shell> tail host_name.log If you find something like the following in the log file: 000729 14:50:10 bdb: Recovery function for LSN 1 27595 failed 000729 14:50:10 bdb: warning: ./test/t1.db: No such file or directory 000729 14:50:10 Can't init databases This means that you didn't start `mysqld' with `--bdb-no-recover' and Berkeley DB found something wrong with its log files when it tried to recover your databases. To be able to continue, you should move away the old Berkeley DB log file from the database directory to some other place, where you can later examine these. The log files are named `log.0000000001', where the number will increase over time. If you are running `mysqld' with BDB table support and `mysqld' core dumps at start this could be because of some problems with the BDB recover log. In this case you can try starting `mysqld' with `--bdb-no-recover'. If this helps, then you should remove all `log.*' files from the data directory and try starting `mysqld' again. If you get the following error, it means that some other program (or another `mysqld' server) is already using the TCP/IP port or socket `mysqld' is trying to use: Can't start server: Bind on TCP/IP port: Address already in use or Can't start server : Bind on unix socket... Use `ps' to make sure that you don't have another `mysqld' server running. If you can't find another server running, you can try to execute the command `telnet your-host-name tcp-ip-port-number' and press `RETURN' a couple of times. If you don't get an error message like `telnet: Unable to connect to remote host: Connection refused', something is using the TCP/IP port `mysqld' is trying to use. See *Note mysql_install_db:: and *Note Multiple servers::. If `mysqld' is currently running, you can find out what path settings it is using by executing this command: shell> mysqladmin variables or shell> mysqladmin -h 'your-host-name' variables If `safe_mysqld' starts the server but you can't connect to it, you should make sure you have an entry in `/etc/hosts' that looks like this: 127.0.0.1 localhost This problem occurs only on systems that don't have a working thread library and for which *MySQL* must be configured to use MIT-pthreads. If you can't get `mysqld' to start you can try to make a trace file to find the problem. *Note Making trace files::. If you are using BDB (Berkeley DB) tables, you should familiarize yourself with the different BDB specific startup options. *Note BDB start::. If you are using Gemini tables, refer to the Gemini-specific startup options. *Note Using GEMINI Tables::. If you are using InnoDB tables, refer to the InnoDB-specific startup options. *Note InnoDB start::. Starting and Stopping MySQL Automatically ----------------------------------------- The `mysql.server' and `safe_mysqld' scripts can be used to start the server automatically at system startup time. `mysql.server' can also be used to stop the server. The `mysql.server' script can be used to start or stop the server by invoking it with `start' or `stop' arguments: shell> mysql.server start shell> mysql.server stop `mysql.server' can be found in the `share/mysql' directory under the *MySQL* installation directory or in the `support-files' directory of the *MySQL* source tree. Before `mysql.server' starts the server, it changes directory to the *MySQL* installation directory, then invokes `safe_mysqld'. You might need to edit `mysql.server' if you have a binary distribution that you've installed in a non-standard location. Modify it to `cd' into the proper directory before it runs `safe_mysqld'. If you want the server to run as some specific user, add an appropriate `user' line to the `/etc/my.cnf' file, as shown later in this section. `mysql.server stop' brings down the server by sending a signal to it. You can take down the server manually by executing `mysqladmin shutdown'. You might want to add these start and stop commands to the appropriate places in your `/etc/rc*' files when you start using *MySQL* for production applications. Note that if you modify `mysql.server', then upgrade *MySQL* sometime, your modified version will be overwritten, so you should make a copy of your edited version that you can reinstall. If your system uses `/etc/rc.local' to start external scripts, you should append the following to it: /bin/sh -c 'cd /usr/local/mysql ; ./bin/safe_mysqld --user=mysql &' You can also add options for `mysql.server' in a global `/etc/my.cnf' file. A typical `/etc/my.cnf' file might look like this: [mysqld] datadir=/usr/local/mysql/var socket=/tmp/mysqld.sock port=3306 user=mysql [mysql.server] basedir=/usr/local/mysql The `mysql.server' script understands the following options: `datadir', `basedir', and `pid-file'. The following table shows which option groups each of the startup scripts read from option files: *Script* *Option groups* `mysqld' `mysqld' and `server' `mysql.server' `mysql.server', `mysqld', and `server' `safe_mysqld' `mysql.server', `mysqld', and `server' *Note Option files::. mysqld Command-line Options --------------------------- `mysqld' accepts the following command-line options: `--ansi' Use ANSI SQL syntax instead of MySQL syntax. *Note ANSI mode::. `-b, --basedir=path' Path to installation directory. All paths are usually resolved relative to this. `--big-tables' Allow big result sets by saving all temporary sets on file. It solves most 'table full' errors, but also slows down the queries where in-memory tables would suffice. Since Version 3.23.2, *MySQL* is able to solve it automatically by using memory for small temporary tables and switching to disk tables where necessary. `--bind-address=IP' IP address to bind to. `--character-sets-dir=path' Directory where character sets are. *Note Character sets::. `--chroot=path' Chroot `mysqld' daemon during startup. Recommended security measure. It will somewhat limit `LOAD DATA INFILE' and `SELECT ... INTO OUTFILE' though. `--core-file' Write a core file if `mysqld' dies. For some systems you must also specify `--core-file-size' to `safe_mysqld'. *Note `safe_mysqld': safe_mysqld. `-h, --datadir=path' Path to the database root. `--default-character-set=charset' Set the default character set. *Note Character sets::. `--default-table-type=type' Set the default table type for tables. *Note Table types::. `--debug[...]=' If *MySQL* is configured with `--with-debug', you can use this option to get a trace file of what `mysqld' is doing. *Note Making trace files::. `--delay-key-write-for-all-tables' Don't flush key buffers between writes for any `MyISAM' table. *Note Server parameters::. `--enable-locking' Enable system locking. Note that if you use this option on a system which a not fully working lockd() (as on Linux) you will easily get mysqld to deadlock. `-T, --exit-info' This is a bit mask of different flags one can use for debugging the mysqld server; One should not use this option if one doesn't know exactly what it does! `--flush' Flush all changes to disk after each SQL command. Normally *MySQL* only does a write of all changes to disk after each SQL command and lets the operating system handle the syncing to disk. *Note Crashing::. `-?, --help' Display short help and exit. `--init-file=file' Read SQL commands from this file at startup. `-L, --language=...' Client error messages in given language. May be given as a full path. *Note Languages::. `-l, --log[=file]' Log connections and queries to file. *Note Query log::. `--log-isam[=file]' Log all ISAM/MyISAM changes to file (only used when debugging ISAM/MyISAM). `--log-slow-queries[=file]' Log all queries that have taken more than `long_query_time' seconds to execute to file. *Note Slow query log::. `--log-update[=file]' Log updates to `file.#' where `#' is a unique number if not given. *Note Update log::. `--log-long-format' Log some extra information to update log. If you are using `--log-slow-queries' then queries that are not using indexes are logged to the slow query log. `--low-priority-updates' Table-modifying operations (`INSERT'/`DELETE'/`UPDATE') will have lower priority than selects. It can also be done via `{INSERT | REPLACE | UPDATE | DELETE} LOW_PRIORITY ...' to lower the priority of only one query, or by `SET OPTION SQL_LOW_PRIORITY_UPDATES=1' to change the priority in one thread. *Note Table locking::. `--memlock' Lock the `mysqld' process in memory. This works only if your system supports the `mlockall()' system call (like Solaris). This may help if you have a problem where the operating system is causing `mysqld' to swap on disk. `--myisam-recover [=option[,option...]]] where option is one of DEFAULT, BACKUP, FORCE or QUICK.' If this option is used, `mysqld' will on open check if the table is marked as crashed or if if the table wasn't closed properly. (The last option only works if you are running with `--skip-locking'). If this is the case `mysqld' will run check on the table. If the table was corrupted, `mysqld' will attempt to repair it. The following options affects how the repair works. DEFAULT The same as not giving any option to `--myisam-recover'. BACKUP If the data table was changed during recover, save a backup of the `table_name.MYD' data file as `table_name-datetime.BAK'. FORCE Run recover even if we will loose more than one row from the .MYD file. QUICK Don't check the rows in the table if there isn't any delete blocks. Before a table is automatically repaired, *MySQL* will add a note about this in the error log. If you want to be able to recover from most things without user intervention, you should use the options `BACKUP,FORCE'. This will force a repair of a table even if some rows would be deleted, but it will keep the old data file as a backup so that you can later examine what happened. `--pid-file=path' Path to pid file used by `safe_mysqld'. `-P, --port=...' Port number to listen for TCP/IP connections. `-o, --old-protocol' Use the 3.20 protocol for compatibility with some very old clients. *Note Upgrading-from-3.20::. `--one-thread' Only use one thread (for debugging under Linux). *Note Debugging server::. `-O, --set-variable var=option' Give a variable a value. `--help' lists variables. You can find a full description for all variables in the `SHOW VARIABLES' section in this manual. *Note SHOW VARIABLES::. The tuning server parameters section includes information of how to optimize these. *Note Server parameters::. `--safe-mode' Skip some optimize stages. Implies `--skip-delay-key-write'. `--safe-show-database' Don't show databases for which the user doesn't have any privileges. `--secure' IP numbers returned by the `gethostbyname()' system call are checked to make sure they resolve back to the original hostname. This makes it harder for someone on the outside to get access by pretending to be another host. This option also adds some sanity checks of hostnames. The option is turned off by default in *MySQL* Version 3.21 because sometimes it takes a long time to perform backward resolutions. *MySQL* Version 3.22 caches hostnames (unless `--skip-host-cache' is used) and has this option enabled by default. `--skip-concurrent-insert' Turn off the ability to select and insert at the same time on `MyISAM' tables. (This is only to be used if you think you have found a bug in this feature). `--skip-delay-key-write' Ignore the `delay_key_write' option for all tables. *Note Server parameters::. `--skip-grant-tables' This option causes the server not to use the privilege system at all. This gives everyone _full access_ to all databases! (You can tell a running server to start using the grant tables again by executing `mysqladmin flush-privileges' or `mysqladmin reload'.) `--skip-host-cache' Never use host name cache for faster name-ip resolution, but query DNS server on every connect instead. *Note DNS::. `--skip-locking' Don't use system locking. To use `isamchk' or `myisamchk' you must shut down the server. *Note Stability::. Note that in *MySQL* Version 3.23 you can use `REPAIR' and `CHECK' to repair/check `MyISAM' tables. `--skip-name-resolve' Hostnames are not resolved. All `Host' column values in the grant tables must be IP numbers or `localhost'. *Note DNS::. `--skip-networking' Don't listen for TCP/IP connections at all. All interaction with `mysqld' must be made via Unix sockets. This option is highly recommended for systems where only local requests are allowed. *Note DNS::. `--skip-new' Don't use new, possible wrong routines. Implies `--skip-delay-key-write'. This will also set default table type to `ISAM'. *Note ISAM::. `--skip-symlink' Don't delete or rename files that a symlinked file in the data directory points to. `--skip-safemalloc' If *MySQL* is configured with `--with-debug=full', all programs will check the memory for overruns for every memory allocation and memory freeing. As this checking is very slow, you can avoid this, when you don't need memory checking, by using this option. `--skip-show-database' Don't allow 'SHOW DATABASE' commands, unless the user has *process* privilege. `--skip-stack-trace' Don't write stack traces. This option is useful when you are running `mysqld' under a debugger. *Note Debugging server::. `--skip-thread-priority' Disable using thread priorities for faster response time. `--socket=path' Socket file to use for local connections instead of default `/tmp/mysql.sock'. `transaction-isolation= { READ-UNCOMMITTED | READ-COMMITTED | REPEATABLE-READ | SERIALIZABLE }' Sets the default transaction isolation level. *Note SET TRANSACTION::. `-t, --tmpdir=path' Path for temporary files. It may be useful if your default `/tmp' directory resides on a partition too small to hold temporary tables. `-u, --user=user_name' Run `mysqld' daemon as user `user_name'. This option is _mandatory_ when starting `mysqld' as root. `-V, --version' Output version information and exit. Option Files ------------ *MySQL* can, since Version 3.22, read default startup options for the server and for clients from option files. *MySQL* reads default options from the following files on Unix: *Filename* *Purpose* `/etc/my.cnf' Global options `DATADIR/my.cnf' Server-specific options `defaults-extra-file' The file specified with -defaults-extra-file=# `~/.my.cnf' User-specific options `DATADIR' is the *MySQL* data directory (typically `/usr/local/mysql/data' for a binary installation or `/usr/local/var' for a source installation). Note that this is the directory that was specified at configuration time, not the one specified with `--datadir' when `mysqld' starts up! (`--datadir' has no effect on where the server looks for option files, because it looks for them before it processes any command-line arguments.) *MySQL* reads default options from the following files on Windows: *Filename* *Purpose* `windows-system-directory\my.ini'Global options `C:\my.cnf' Global options `C:\mysql\data\my.cnf' Server-specific options Note that on Windows, you should specify all paths with `/' instead of `\'. If you use `\', you need to specify this twice, as `\' is the escape character in *MySQL*. *MySQL* tries to read option files in the order listed above. If multiple option files exist, an option specified in a file read later takes precedence over the same option specified in a file read earlier. Options specified on the command line take precedence over options specified in any option file. Some options can be specified using environment variables. Options specified on the command line or in option files take precedence over environment variable values. *Note Environment variables::. The following programs support option files: `mysql', `mysqladmin', `mysqld', `mysqldump', `mysqlimport', `mysql.server', `myisamchk', and `myisampack'. You can use option files to specify any long option that a program supports! Run the program with `--help' to get a list of available options. An option file can contain lines of the following forms: `#comment' Comment lines start with `#' or `;'. Empty lines are ignored. `[group]' `group' is the name of the program or group for which you want to set options. After a group line, any `option' or `set-variable' lines apply to the named group until the end of the option file or another group line is given. `option' This is equivalent to `--option' on the command line. `option=value' This is equivalent to `--option=value' on the command line. `set-variable = variable=value' This is equivalent to `--set-variable variable=value' on the command line. This syntax must be used to set a `mysqld' variable. The `client' group allows you to specify options that apply to all *MySQL* clients (not `mysqld'). This is the perfect group to use to specify the password you use to connect to the server. (But make sure the option file is readable and writable only by yourself.) Note that for options and values, all leading and trailing blanks are automatically deleted. You may use the escape sequences `\b', `\t', `\n', `\r', `\\', and `\s' in your value string (`\s' == blank). Here is a typical global option file: [client] port=3306 socket=/tmp/mysql.sock [mysqld] port=3306 socket=/tmp/mysql.sock set-variable = key_buffer_size=16M set-variable = max_allowed_packet=1M [mysqldump] quick Here is typical user option file: [client] # The following password will be sent to all standard MySQL clients password=my_password [mysql] no-auto-rehash set-variable = connect_timeout=2 [mysqlhotcopy] interactive-timeout If you have a source distribution, you will find sample configuration files named `my-xxxx.cnf' in the `support-files' directory. If you have a binary distribution, look in the `DIR/support-files' directory, where `DIR' is the pathname to the *MySQL* installation directory (typically `/usr/local/mysql'). Currently there are sample configuration files for small, medium, large, and very large systems. You can copy `my-xxxx.cnf' to your home directory (rename the copy to `.my.cnf') to experiment with this. All *MySQL* clients that support option files support the following options: -no-defaults Don't read any option files. -print-defaults Print the program name and all options that it will get. -defaults-file=full-path-to-default-fileOnly use the given configuration file. -defaults-extra-file=full-path-to-default-fileRead this configuration file after the global configuration file but before the user configuration file. Note that the above options must be first on the command line to work! `--print-defaults' may however be used directly after the `--defaults-xxx-file' commands. Note for developers: Option file handling is implemented simply by processing all matching options (that is, options in the appropriate group) before any command-line arguments. This works nicely for programs that use the last instance of an option that is specified multiple times. If you have an old program that handles multiply-specified options this way but doesn't read option files, you need add only two lines to give it that capability. Check the source code of any of the standard *MySQL* clients to see how to do this. In shell scripts you can use the `my_print_defaults' command to parse the config files: shell> my_print_defaults client mysql --port=3306 --socket=/tmp/mysql.sock --no-auto-rehash The above output contains all options for the groups 'client' and 'mysql'. Installing Many Servers on the Same Machine =========================================== In some cases you may want to have many different `mysqld' daemons (servers) running on the same machine. You may for example want to run a new version of *MySQL* for testing together with an old version that is in production. Another case is when you want to give different users access to different `mysqld' servers that they manage themselves. One way to get a new server running is by starting it with a different socket and port as follows: shell> MYSQL_UNIX_PORT=/tmp/mysqld-new.sock shell> MYSQL_TCP_PORT=3307 shell> export MYSQL_UNIX_PORT MYSQL_TCP_PORT shell> scripts/mysql_install_db shell> bin/safe_mysqld & The environment variables appendix includes a list of other environment variables you can use to affect `mysqld'. *Note Environment variables::. The above is the quick and dirty way that one commonly uses for testing. The nice thing with this is that all connections you do in the above shell will automatically be directed to the new running server! If you need to do this more permanently, you should create an option file for each server. *Note Option files::. In your startup script that is executed at boot time (mysql.server?) you should specify for both servers: `safe_mysqld --default-file=path-to-option-file' At least the following options should be different per server: `port=#' `socket=path' `pid-file=path' The following options should be different, if they are used: `log=path' `log-bin=path' `log-update=path' `log-isam=path' `bdb-logdir=path' If you want more performance, you can also specify the following differently: `tmpdir=path' `bdb-tmpdir=path' *Note Command-line options::. If you are installing binary *MySQL* versions (.tar files) and start them with `./bin/safe_mysqld' then in most cases the only option you need to add/change is the `socket' and `port' argument to `safe_mysqld'. Upgrading/Downgrading MySQL =========================== You can always move the *MySQL* form and data files between different versions on the same architecture as long as you have the same base version of *MySQL*. The current base version is 3. If you change the character set when running *MySQL* (which may also change the sort order), you must run `myisamchk -r -q' on all tables. Otherwise your indexes may not be ordered correctly. If you are afraid of new versions, you can always rename your old `mysqld' to something like `mysqld'-'old-version-number'. If your new `mysqld' then does something unexpected, you can simply shut it down and restart with your old `mysqld'! When you do an upgrade you should also back up your old databases, of course. If after an upgrade, you experience problems with recompiled client programs, like `Commands out of sync' or unexpected core dumps, you probably have used an old header or library file when compiling your programs. In this case you should check the date for your `mysql.h' file and `libmysqlclient.a' library to verify that they are from the new *MySQL* distribution. If not, please recompile your programs! If you get some problems that the new `mysqld' server doesn't want to start or that you can't connect without a password, check that you don't have some old `my.cnf' file from your old installation! You can check this with: `program-name --print-defaults'. If this outputs anything other than the program name, you have an active `my.cnf' file that will affect things! It is a good idea to rebuild and reinstall the `Msql-Mysql-modules' distribution whenever you install a new release of *MySQL*, particularly if you notice symptoms such as all your `DBI' scripts dumping core after you upgrade *MySQL*. Upgrading From Version 3.22 to Version 3.23 ------------------------------------------- *MySQL* Version 3.23 supports tables of the new `MyISAM' type and the old `ISAM' type. You don't have to convert your old tables to use these with Version 3.23. By default, all new tables will be created with type `MyISAM' (unless you start `mysqld' with the `--default-table-type=isam' option). You can change an `ISAM' table to a `MyISAM' table with `ALTER TABLE table_name TYPE=MyISAM' or the Perl script `mysql_convert_table_format'. Version 3.22 and 3.21 clients will work without any problems with a Version 3.23 server. The following lists tell what you have to watch out for when upgrading to Version 3.23: * All tables that uses the `tis620' character set must be fixed with `myisamchk -r' or `REPAIR TABLE'. * If you do a `DROP DATABASE' on a symbolic linked database, both the link and the original database is deleted. (This didn't happen in 3.22 because configure didn't detect the `readlink' system call). * `OPTIMIZE TABLE' now only works for *MyISAM* tables. For other table types, you can use `ALTER TABLE' to optimize the table. During `OPTIMIZE TABLE' the table is now locked from other threads. * The *MySQL* client `mysql' is now by default started with the option `--no-named-commands (-g)'. This option can be disabled with `--enable-named-commands (-G)'. This may cause incompatibility problems in some cases, for example in SQL scripts that use named commands without a semicolon! Long format commands still work from the first line. * If you are using the `german' character sort order, you must repair all your tables with `isamchk -r', as we have made some changes in the sort order! * The default return type of `IF' will now depend on both arguments and not only the first argument. * `AUTO_INCREMENT' will not work with negative numbers. The reason for this is that negative numbers caused problems when wrapping from -1 to 0. `AUTO_INCREMENT' is now for MyISAM tables handled at a lower level and is much faster than before. For MyISAM tables old numbers are also not reused anymore, even if you delete some rows from the table. * `CASE', `DELAYED', `ELSE', `END', `FULLTEXT', `INNER', `RIGHT', `THEN' and `WHEN' are now reserved words. * `FLOAT(X)' is now a true floating-point type and not a value with a fixed number of decimals. * When declaring `DECIMAL(length,dec)' the length argument no longer includes a place for the sign or the decimal point. * A `TIME' string must now be of one of the following formats: `[[[DAYS] [H]H:]MM:]SS[.fraction]' or `[[[[[H]H]H]H]MM]SS[.fraction]' * `LIKE' now compares strings using the same character comparison rules as `'=''. If you require the old behavior, you can compile *MySQL* with the `CXXFLAGS=-DLIKE_CMP_TOUPPER' flag. * `REGEXP' is now case insensitive for normal (not binary) strings. * When you check/repair tables you should use `CHECK TABLE' or `myisamchk' for `MyISAM' tables (`.MYI') and `isamchk' for ISAM (`.ISM') tables. * If you want your `mysqldump' files to be compatible between *MySQL* Version 3.22 and Version 3.23, you should not use the `--opt' or `--full' option to `mysqldump'. * Check all your calls to `DATE_FORMAT()' to make sure there is a `%' before each format character. (Later *MySQL* Version 3.22 did allow this syntax.) * `mysql_fetch_fields_direct' is now a function (it was a macro) and it returns a pointer to a `MYSQL_FIELD' instead of a `MYSQL_FIELD'. * `mysql_num_fields()' can no longer be used on a `MYSQL*' object (it's now a function that takes `MYSQL_RES*' as an argument. You should now use `mysql_field_count()' instead. * In *MySQL* Version 3.22, the output of `SELECT DISTINCT ...' was almost always sorted. In Version 3.23, you must use `GROUP BY' or `ORDER BY' to obtain sorted output. * `SUM()' now returns `NULL', instead of 0, if there is no matching rows. This is according to ANSI SQL. * An `AND' or `OR' with `NULL' values will now return `NULL' instead of 0. This mostly affects queries that use `NOT' on an `AND/OR' expression as `NOT NULL' = `NULL'. `LPAD()' and `RPAD()' will shorten the result string if it's longer than the length argument. Upgrading from Version 3.21 to Version 3.22 ------------------------------------------- Nothing that affects compatibility has changed between Version 3.21 and 3.22. The only pitfall is that new tables that are created with `DATE' type columns will use the new way to store the date. You can't access these new fields from an old version of `mysqld'. After installing *MySQL* Version 3.22, you should start the new server and then run the `mysql_fix_privilege_tables' script. This will add the new privileges that you need to use the `GRANT' command. If you forget this, you will get `Access denied' when you try to use `ALTER TABLE', `CREATE INDEX', or `DROP INDEX'. If your *MySQL* root user requires a password, you should give this as an argument to `mysql_fix_privilege_tables'. The C API interface to `mysql_real_connect()' has changed. If you have an old client program that calls this function, you must place a `0' for the new `db' argument (or recode the client to send the `db' element for faster connections). You must also call `mysql_init()' before calling `mysql_real_connect()'! This change was done to allow the new `mysql_options()' function to save options in the `MYSQL' handler structure. The `mysqld' variable `key_buffer' has changed names to `key_buffer_size', but you can still use the old name in your startup files. Upgrading from Version 3.20 to Version 3.21 ------------------------------------------- If you are running a version older than Version 3.20.28 and want to switch to Version 3.21, you need to do the following: You can start the `mysqld' Version 3.21 server with `safe_mysqld --old-protocol' to use it with clients from a Version 3.20 distribution. In this case, the new client function `mysql_errno()' will not return any server error, only `CR_UNKNOWN_ERROR' (but it works for client errors), and the server uses the old `password()' checking rather than the new one. If you are *NOT* using the `--old-protocol' option to `mysqld', you will need to make the following changes: * All client code must be recompiled. If you are using ODBC, you must get the new *MyODBC* 2.x driver. * The script `scripts/add_long_password' must be run to convert the `Password' field in the `mysql.user' table to `CHAR(16)'. * All passwords must be reassigned in the `mysql.user' table (to get 62-bit rather than 31-bit passwords). * The table format hasn't changed, so you don't have to convert any tables. *MySQL* Version 3.20.28 and above can handle the new `user' table format without affecting clients. If you have a *MySQL* version earlier than Version 3.20.28, passwords will no longer work with it if you convert the `user' table. So to be safe, you should first upgrade to at least Version 3.20.28 and then upgrade to Version 3.21. The new client code works with a 3.20.x `mysqld' server, so if you experience problems with 3.21.x, you can use the old 3.20.x server without having to recompile the clients again. If you are not using the `--old-protocol' option to `mysqld', old clients will issue the error message: ERROR: Protocol mismatch. Server Version = 10 Client Version = 9 The new Perl `DBI'/`DBD' interface also supports the old `mysqlperl' interface. The only change you have to make if you use `mysqlperl' is to change the arguments to the `connect()' function. The new arguments are: `host', `database', `user', `password' (the `user' and `password' arguments have changed places). *Note Perl `DBI' Class: Perl DBI Class. The following changes may affect queries in old applications: * `HAVING' must now be specified before any `ORDER BY' clause. * The parameters to `LOCATE()' have been swapped. * There are some new reserved words. The most notable are `DATE', `TIME', and `TIMESTAMP'. Upgrading to Another Architecture --------------------------------- If you are using *MySQL* Version 3.23, you can copy the `.frm', `.MYI', and `.MYD' files between different architectures that support the same floating-point format. (*MySQL* takes care of any byte swapping issues.) The *MySQL* `ISAM' data and index files (`.ISD' and `*.ISM', respectively) are architecture-dependent and in some cases OS-dependent. If you want to move your applications to another machine that has a different architecture or OS than your current machine, you should not try to move a database by simply copying the files to the other machine. Use `mysqldump' instead. By default, `mysqldump' will create a file full of SQL statements. You can then transfer the file to the other machine and feed it as input to the `mysql' client. Try `mysqldump --help' to see what options are available. If you are moving the data to a newer version of *MySQL*, you should use `mysqldump --opt' with the newer version to get a fast, compact dump. The easiest (although not the fastest) way to move a database between two machines is to run the following commands on the machine on which the database is located: shell> mysqladmin -h 'other hostname' create db_name shell> mysqldump --opt db_name \ | mysql -h 'other hostname' db_name If you want to copy a database from a remote machine over a slow network, you can use: shell> mysqladmin create db_name shell> mysqldump -h 'other hostname' --opt --compress db_name \ | mysql db_name You can also store the result in a file, then transfer the file to the target machine and load the file into the database there. For example, you can dump a database to a file on the source machine like this: shell> mysqldump --quick db_name | gzip > db_name.contents.gz (The file created in this example is compressed.) Transfer the file containing the database contents to the target machine and run these commands there: shell> mysqladmin create db_name shell> gunzip < db_name.contents.gz | mysql db_name You can also use `mysqldump' and `mysqlimport' to accomplish the database transfer. For big tables, this is much faster than simply using `mysqldump'. In the commands shown below, `DUMPDIR' represents the full pathname of the directory you use to store the output from `mysqldump'. First, create the directory for the output files and dump the database: shell> mkdir DUMPDIR shell> mysqldump --tab=DUMPDIR db_name Then transfer the files in the `DUMPDIR' directory to some corresponding directory on the target machine and load the files into *MySQL* there: shell> mysqladmin create db_name # create database shell> cat DUMPDIR/*.sql | mysql db_name # create tables in database shell> mysqlimport db_name DUMPDIR/*.txt # load data into tables Also, don't forget to copy the `mysql' database, because that's where the grant tables (`user', `db', `host') are stored. You may have to run commands as the *MySQL* `root' user on the new machine until you have the `mysql' database in place. After you import the `mysql' database on the new machine, execute `mysqladmin flush-privileges' so that the server reloads the grant table information. How Standards-compatible Is MySQL? ********************************** This chapter describes how *MySQL* relates to the ANSI SQL standards. *MySQL* has many extensions to the ANSI SQL standards, and here you will find out what they are, and how to use them. You will also find information about functionality missing from *MySQL*, and how to work around some differences. MySQL Extensions to ANSI SQL92 ============================== *MySQL* includes some extensions that you probably will not find in other SQL databases. Be warned that if you use them, your code will not be portable to other SQL servers. In some cases, you can write code that includes *MySQL* extensions, but is still portable, by using comments of the form `/*! ... */'. In this case, *MySQL* will parse and execute the code within the comment as it would any other *MySQL* statement, but other SQL servers will ignore the extensions. For example: SELECT /*! STRAIGHT_JOIN */ col_name FROM table1,table2 WHERE ... If you add a version number after the `'!'', the syntax will only be executed if the *MySQL* version is equal to or newer than the used version number: CREATE /*!32302 TEMPORARY */ TABLE (a int); The above means that if you have Version 3.23.02 or newer, then *MySQL* will use the `TEMPORARY' keyword. *MySQL* extensions are listed below: * The field types `MEDIUMINT', `SET', `ENUM', and the different `BLOB' and `TEXT' types. * The field attributes `AUTO_INCREMENT', `BINARY', `NULL', `UNSIGNED', and `ZEROFILL'. * All string comparisons are case insensitive by default, with sort ordering determined by the current character set (ISO-8859-1 Latin1 by default). If you don't like this, you should declare your columns with the `BINARY' attribute or use the `BINARY' cast, which causes comparisons to be done according to the ASCII order used on the *MySQL* server host. * *MySQL* maps each database to a directory under the *MySQL* data directory, and tables within a database to filenames in the database directory. This has a few implications: - Database names and table names are case sensitive in *MySQL* on operating systems that have case-sensitive filenames (like most Unix systems). *Note Name case sensitivity::. - Database, table, index, column, or alias names may begin with a digit (but may not consist solely of digits). - You can use standard system commands to backup, rename, move, delete, and copy tables. For example, to rename a table, rename the `.MYD', `.MYI', and `.frm' files to which the table corresponds. * In SQL statements, you can access tables from different databases with the `db_name.tbl_name' syntax. Some SQL servers provide the same functionality but call this `User space'. *MySQL* doesn't support tablespaces as in: `create table ralph.my_table...IN my_tablespace'. * `LIKE' is allowed on numeric columns. * Use of `INTO OUTFILE' and `STRAIGHT_JOIN' in a `SELECT' statement. *Note `SELECT': SELECT. * The `SQL_SMALL_RESULT' option in a `SELECT' statement. * `EXPLAIN SELECT' to get a description on how tables are joined. * Use of index names, indexes on a prefix of a field, and use of `INDEX' or `KEY' in a `CREATE TABLE' statement. *Note `CREATE TABLE': CREATE TABLE. * Use of `TEMPORARY' or `IF NOT EXISTS' with `CREATE TABLE'. * Use of `COUNT(DISTINCT list)' where 'list' is more than one element. * Use of `CHANGE col_name', `DROP col_name', or `DROP INDEX', `IGNORE' or `RENAME' in an `ALTER TABLE' statement. *Note `ALTER TABLE': ALTER TABLE. * Use of `RENAME TABLE'. *Note `RENAME TABLE': RENAME TABLE. * Use of multiple `ADD', `ALTER', `DROP', or `CHANGE' clauses in an `ALTER TABLE' statement. * Use of `DROP TABLE' with the keywords `IF EXISTS'. * You can drop multiple tables with a single `DROP TABLE' statement. * The `LIMIT' clause of the `DELETE' statement. * The `DELAYED' clause of the `INSERT' and `REPLACE' statements. * The `LOW_PRIORITY' clause of the `INSERT', `REPLACE', `DELETE', and `UPDATE' statements. * Use of `LOAD DATA INFILE'. In many cases, this syntax is compatible with Oracle's `LOAD DATA INFILE'. *Note `LOAD DATA': LOAD DATA. * The `ANALYZE TABLE', `CHECK TABLE', `OPTIMIZE TABLE', and `REPAIR TABLE' statements. * The `SHOW' statement. *Note `SHOW': SHOW. * Strings may be enclosed by either `"' or `'', not just by `''. * Use of the escape `\' character. * The `SET OPTION' statement. *Note `SET OPTION': SET OPTION. * You don't need to name all selected columns in the `GROUP BY' part. This gives better performance for some very specific, but quite normal queries. *Note Group by functions::. * One can specify `ASC' and `DESC' with `GROUP BY'. * To make it easier for users who come from other SQL environments, *MySQL* supports aliases for many functions. For example, all string functions support both ANSI SQL syntax and ODBC syntax. * *MySQL* understands the `||' and `&&' operators to mean logical OR and AND, as in the C programming language. In *MySQL*, `||' and `OR' are synonyms, as are `&&' and `AND'. Because of this nice syntax, *MySQL* doesn't support the ANSI SQL `||' operator for string concatenation; use `CONCAT()' instead. Because `CONCAT()' takes any number of arguments, it's easy to convert use of the `||' operator to *MySQL*. * `CREATE DATABASE' or `DROP DATABASE'. *Note `CREATE DATABASE': CREATE DATABASE. * The `%' operator is a synonym for `MOD()'. That is, `N % M' is equivalent to `MOD(N,M)'. `%' is supported for C programmers and for compatibility with PostgreSQL. * The `=', `<>', `<=' ,`<', `>=',`>', `<<', `>>', `<=>', `AND', `OR', or `LIKE' operators may be used in column comparisons to the left of the `FROM' in `SELECT' statements. For example: mysql> SELECT col1=1 AND col2=2 FROM tbl_name; * The `LAST_INSERT_ID()' function. *Note `mysql_insert_id()': mysql_insert_id. * The `REGEXP' and `NOT REGEXP' extended regular expression operators. * `CONCAT()' or `CHAR()' with one argument or more than two arguments. (In *MySQL*, these functions can take any number of arguments.) * The `BIT_COUNT()', `CASE', `ELT()', `FROM_DAYS()', `FORMAT()', `IF()', `PASSWORD()', `ENCRYPT()', `md5()', `ENCODE()', `DECODE()', `PERIOD_ADD()', `PERIOD_DIFF()', `TO_DAYS()', or `WEEKDAY()' functions. * Use of `TRIM()' to trim substrings. ANSI SQL only supports removal of single characters. * The `GROUP BY' functions `STD()', `BIT_OR()', and `BIT_AND()'. * Use of `REPLACE' instead of `DELETE' + `INSERT'. *Note `REPLACE': REPLACE. * The `FLUSH flush_option' statement. * The possibility to set variables in a statement with `:=': SELECT @a:=SUM(total),@b=COUNT(*),@a/@b AS avg FROM test_table; SELECT @t1:=(@t2:=1)+@t3:=4,@t1,@t2,@t3; Running MySQL in ANSI Mode ========================== If you start `mysqld' with the `--ansi' option, the following behavior of *MySQL* changes: * `||' is string concatenation instead of `OR'. * You can have any number of spaces between a function name and the `('. This forces all function names to be treated as reserved words. * `"' will be an identifier quote character (like the *MySQL* ``' quote character) and not a string quote character. * `REAL' will be a synonym for `FLOAT' instead of a synonym of `DOUBLE'. * The default transaction isolation level is `SERIALIZABLE'. *Note SET TRANSACTION::. MySQL Differences Compared to ANSI SQL92 ======================================== We try to make *MySQL* follow the ANSI SQL standard and the ODBC SQL standard, but in some cases *MySQL* does some things differently: * `--' is only a comment if followed by a white space. *Note Missing comments::. * For `VARCHAR' columns, trailing spaces are removed when the value is stored. *Note Bugs::. * In some cases, `CHAR' columns are silently changed to `VARCHAR' columns. *Note Silent column changes::. * Privileges for a table are not automatically revoked when you delete a table. You must explicitly issue a `REVOKE' to revoke privileges for a table. *Note `GRANT': GRANT. * `NULL AND FALSE' will evaluate to `NULL' and not to `FALSE'. This is because we don't think it's good to have to evaluate a lot of extra conditions in this case. Functionality Missing from MySQL ================================ The following functionality is missing in the current version of *MySQL*. For a prioritized list indicating when new extensions may be added to *MySQL*, you should consult the online *MySQL* TODO list (http://www.mysql.com/documentation/manual.php?section=TODO). That is the latest version of the TODO list in this manual. *Note TODO::. Sub-selects ----------- The following will not yet work in *MySQL*: SELECT * FROM table1 WHERE id IN (SELECT id FROM table2); SELECT * FROM table1 WHERE id NOT IN (SELECT id FROM table2); SELECT * FROM table1 WHERE NOT EXISTS (SELECT id FROM table2 where table1.id=table2.id); However, in many cases you can rewrite the query without a sub-select: SELECT table1.* FROM table1,table2 WHERE table1.id=table2.id; SELECT table1.* FROM table1 LEFT JOIN table2 ON table1.id=table2.id where table2.id IS NULL For more complicated subqueries you can often create temporary tables to hold the subquery. In some cases, however this option will not work. The most frequently encountered of these cases arises with `DELETE' statements, for which standard SQL does not support joins (except in sub-selects). For this situation there are two options available until subqueries are supported by *MySQL*. The first option is to use a procedural programming language (such as Perl or PHP) to submit a `SELECT' query to obtain the primary keys for the records to be deleted, and then use these values to construct the `DELETE' statement (`DELETE FROM ... WHERE ... IN (key1, key2, ...)'). The second option is to use interactive SQL to contruct a set of `DELETE' statements automatically, using the *MySQL* extension `CONCAT()' (in lieu of the standard `||' operator). For example: SELECT CONCAT('DELETE FROM tab1 WHERE pkid = ', tab1.pkid, ';') FROM tab1, tab2 WHERE tab1.col1 = tab2.col2; You can place this query in a script file and redirect input from it to the `mysql' command-line interpreter, piping its output back to a second instance of the interpreter: prompt> mysql --skip-column-names mydb < myscript.sql | mysql mydb *MySQL* only supports `INSERT ... SELECT ...' and `REPLACE ... SELECT ...' Independent sub-selects will probably be available in Version 4.0. You can now use the function `IN()' in other contexts, however. `SELECT INTO TABLE' ------------------- *MySQL* doesn't yet support the Oracle SQL extension: `SELECT ... INTO TABLE ...'. *MySQL* supports instead the ANSI SQL syntax `INSERT INTO ... SELECT ...', which is basically the same thing. *Note INSERT SELECT::. INSERT INTO tblTemp2 (fldID) SELECT tblTemp1.fldOrder_ID FROM tblTemp1 WHERE tblTemp1.fldOrder_ID > 100; Alternatively, you can use `SELECT INTO OUTFILE...' or `CREATE TABLE ... SELECT' to solve your problem. Transactions ------------ As *MySQL* does nowadays support transactions, the following discussion is only valid if you are only using the non-transaction-safe table types. *Note COMMIT::. The question is often asked, by the curious and the critical, "Why is *MySQL* not a transactional database?" or "Why does *MySQL* not support transactions?" *MySQL* has made a conscious decision to support another paradigm for data integrity, "atomic operations." It is our thinking and experience that atomic operations offer equal or even better integrity with much better performance. We, nonetheless, appreciate and understand the transactional database paradigm and plan, within the next few releases, to introduce transaction-safe tables on a per table basis. We will be giving our users the possibility to decide if they need the speed of atomic operations or if they need to use transactional features in their applications. How does one use the features of *MySQL* to maintain rigorous integrity and how do these features compare with the transactional paradigm? First, in the transactional paradigm, if your applications are written in a way that is dependent on the calling of "rollback" instead of "commit" in critical situations, then transactions are more convenient. Moreover, transactions ensure that unfinished updates or corrupting activities are not committed to the database; the server is given the opportunity to do an automatic rollback and your database is saved. *MySQL*, in almost all cases, allows you to solve for potential problems by including simple checks before updates and by running simple scripts that check the databases for inconsistencies and automatically repair or warn if such occurs. Note that just by using the *MySQL* log or even adding one extra log, one can normally fix tables perfectly with no data integrity loss. Moreover, fatal transactional updates can be rewritten to be atomic. In fact,we will go so far as to say that all integrity problems that transactions solve can be done with `LOCK TABLES' or atomic updates, ensuring that you never will get an automatic abort from the database, which is a common problem with transactional databases. Not even transactions can prevent all loss if the server goes down. In such cases even a transactional system can lose data. The difference between different systems lies in just how small the time-lap is where they could lose data. No system is 100% secure, only "secure enough." Even Oracle, reputed to be the safest of transactional databases, is reported to sometimes lose data in such situations. To be safe with *MySQL*, you only need to have backups and have the update logging turned on. With this you can recover from any situation that you could with any transactional database. It is, of course, always good to have backups, independent of which database you use. The transactional paradigm has its benefits and its drawbacks. Many users and application developers depend on the ease with which they can code around problems where an abort appears to be, or is necessary, and they may have to do a little more work with *MySQL* to either think differently or write more. If you are new to the atomic operations paradigm, or more familiar or more comfortable with transactions, do not jump to the conclusion that *MySQL* has not addressed these issues. Reliability and integrity are foremost in our minds. Recent estimates indicate that there are more than 1,000,000 `mysqld' servers currently running, many of which are in production environments. We hear very, very seldom from our users that they have lost any data, and in almost all of those cases user error is involved. This is, in our opinion, the best proof of *MySQL*'s stability and reliability. Lastly, in situations where integrity is of highest importance, *MySQL*'s current features allow for transaction-level or better reliability and integrity. If you lock tables with `LOCK TABLES', all updates will stall until any integrity checks are made. If you only obtain a read lock (as opposed to a write lock), then reads and inserts are still allowed to happen. The new inserted records will not be seen by any of the clients that have a `READ' lock until they release their read locks. With `INSERT DELAYED' you can queue inserts into a local queue, until the locks are released, without having the client wait for the insert to complete. *Note INSERT DELAYED::. "Atomic," in the sense that we mean it, is nothing magical. It only means that you can be sure that while each specific update is running, no other user can interfere with it, and there will never be an automatic rollback (which can happen on transaction based systems if you are not very careful). *MySQL* also guarantees that there will not be any dirty reads. You can find some example of how to write atomic updates in the commit-rollback section. *Note Commit-rollback::. We have thought quite a bit about integrity and performance, and we believe that our atomic operations paradigm allows for both high reliability and extremely high performance, on the order of three to five times the speed of the fastest and most optimally tuned of transactional databases. We didn't leave out transactions because they are hard to do. The main reason we went with atomic operations as opposed to transactions is that by doing this we could apply many speed optimizations that would not otherwise have been possible. Many of our users who have speed foremost in their minds are not at all concerned about transactions. For them transactions are not an issue. For those of our users who are concerned with or have wondered about transactions vis-a-vis *MySQL*, there is a "*MySQL* way" as we have outlined above. For those where safety is more important than speed, we recommend them to use the `BDB', `GEMINI' or `InnoDB' tables for all their critical data. *Note Table types::. One final note: We are currently working on a safe replication schema that we believe to be better than any commercial replication system we know of. This system will work most reliably under the atomic operations, non-transactional, paradigm. Stay tuned. Stored Procedures and Triggers ------------------------------ A stored procedure is a set of SQL commands that can be compiled and stored in the server. Once this has been done, clients don't need to keep reissuing the entire query but can refer to the stored procedure. This provides better performance because the query has to be parsed only once, and less information needs to be sent between the server and the client. You can also raise the conceptual level by having libraries of functions in the server. A trigger is a stored procedure that is invoked when a particular event occurs. For example, you can install a stored procedure that is triggered each time a record is deleted from a transaction table and that automatically deletes the corresponding customer from a customer table when all his transactions are deleted. The planned update language will be able to handle stored procedures, but without triggers. Triggers usually slow down everything, even queries for which they are not needed. To see when *MySQL* might get stored procedures, see *Note TODO::. Foreign Keys ------------ Note that foreign keys in SQL are not used to join tables, but are used mostly for checking referential integrity (foreign key constraints). If you want to get results from multiple tables from a `SELECT' statement, you do this by joining tables: SELECT * from table1,table2 where table1.id = table2.id; *Note `JOIN': JOIN. *Note example-Foreign keys::. The `FOREIGN KEY' syntax in *MySQL* exists only for compatibility with other SQL vendors' `CREATE TABLE' commands; it doesn't do anything. The `FOREIGN KEY' syntax without `ON DELETE ...' is mostly used for documentation purposes. Some ODBC applications may use this to produce automatic `WHERE' clauses, but this is usually easy to override. `FOREIGN KEY' is sometimes used as a constraint check, but this check is unnecessary in practice if rows are inserted into the tables in the right order. *MySQL* only supports these clauses because some applications require them to exist (regardless of whether or not they work). In *MySQL*, you can work around the problem of `ON DELETE ...' not being implemented by adding the appropriate `DELETE' statement to an application when you delete records from a table that has a foreign key. In practice this is as quick (in some cases quicker) and much more portable than using foreign keys. In the near future we will extend the `FOREIGN KEY' implementation so that at least the information will be saved in the table specification file and may be retrieved by `mysqldump' and ODBC. At a later stage we will implement the foreign key constraints for application that can't easily be coded to avoid them. Reasons NOT to Use Foreign Keys constraints ........................................... There are so many problems with foreign key constraints that we don't know where to start: * Foreign key constraints make life very complicated, because the foreign key definitions must be stored in a database and implementing them would destroy the whole "nice approach" of using files that can be moved, copied, and removed. * The speed impact is terrible for `INSERT' and `UPDATE' statements, and in this case almost all `FOREIGN KEY' constraint checks are useless because you usually insert records in the right tables in the right order, anyway. * There is also a need to hold locks on many more tables when updating one table, because the side effects can cascade through the entire database. It's MUCH faster to delete records from one table first and subsequently delete them from the other tables. * You can no longer restore a table by doing a full delete from the table and then restoring all records (from a new source or from a backup). * If you use foreign key constraints you can't dump and restore tables unless you do so in a very specific order. * It's very easy to do "allowed" circular definitions that make the tables impossible to re-create each table with a single create statement, even if the definition works and is usable. * It's very easy to overlook `FOREIGN KEY ... ON DELETE' rules when one codes an application. It's not unusual that one loses a lot of important information just because a wrong or misused `ON DELETE' rule. The only nice aspect of `FOREIGN KEY' is that it gives ODBC and some other client programs the ability to see how a table is connected and to use this to show connection diagrams and to help in building applications. *MySQL* will soon store `FOREIGN KEY' definitions so that a client can ask for and receive an answer about how the original connection was made. The current `.frm' file format does not have any place for it. At a later stage we will implement the foreign key constraints for application that can't easily be coded to avoid them. Views ----- *MySQL* doesn't yet support views, but we plan to implement these to about 4.1. Views are mostly useful for letting users access a set of relations as one table (in read-only mode). Many SQL databases don't allow one to update any rows in a view, but you have to do the updates in the separate tables. As *MySQL* is mostly used in applications and on web system where the application writer has full control on the database usage, most of our users haven't regarded views to be very important. (At least no one has been interested enough in this to be prepared to finance the implementation of views). One doesn't need views in *MySQL* to restrict access to columns as *MySQL* has a very sophisticated privilege system. *Note Privilege system::. `--' as the Start of a Comment ------------------------------ Some other SQL databases use `--' to start comments. *MySQL* has `#' as the start comment character, even if the `mysql' command-line tool removes all lines that start with `--'. You can also use the C comment style `/* this is a comment */' with *MySQL*. *Note Comments::. *MySQL* Version 3.23.3 and above supports the `--' comment style only if the comment is followed by a space. This is because this degenerate comment style has caused many problems with automatically generated SQL queries that have used something like the following code, where we automatically insert the value of the payment for `!payment!': UPDATE tbl_name SET credit=credit-!payment! What do you think will happen when the value of `payment' is negative? Because `1--1' is legal in SQL, we think it is terrible that `--' means start comment. In *MySQL* Version 3.23 you can, however, use: `1-- This is a comment' The following discussion only concerns you if you are running a *MySQL* version earlier than Version 3.23: If you have a SQL program in a text file that contains `--' comments you should use: shell> replace " --" " #" < text-file-with-funny-comments.sql \ | mysql database instead of the usual: shell> mysql database < text-file-with-funny-comments.sql You can also edit the command file "in place" to change the `--' comments to `#' comments: shell> replace " --" " #" -- text-file-with-funny-comments.sql Change them back with this command: shell> replace " #" " --" -- text-file-with-funny-comments.sql What Standards Does MySQL Follow? ================================= Entry level SQL92. ODBC levels 0-2. How to Cope Without `COMMIT'/`ROLLBACK' ======================================= The following mostly applies only for `ISAM', `MyISAM', and `HEAP' tables. If you only use transaction-safe tables (`BDB', `GEMINI' or `InnoDB' tables) in an an update, you can do `COMMIT' and `ROLLBACK' also with *MySQL*. *Note COMMIT::. The problem with handling `COMMIT'-`ROLLBACK' efficiently with the above table types would require a completely different table layout than *MySQL* uses today. The table type would also need extra threads that do automatic cleanups on the tables, and the disk usage would be much higher. This would make these table types about 2-4 times slower than they are today. For the moment, we prefer implementing the SQL server language (something like stored procedures). With this you would very seldom really need `COMMIT'-`ROLLBACK.' This would also give much better performance. Loops that need transactions normally can be coded with the help of `LOCK TABLES', and you don't need cursors when you can update records on the fly. We at TcX had a greater need for a real fast database than a 100% general database. Whenever we find a way to implement these features without any speed loss, we will probably do it. For the moment, there are many more important things to do. Check the TODO for how we prioritize things at the moment. (Customers with higher levels of support can alter this, so things may be reprioritized.) The current problem is actually `ROLLBACK'. Without `ROLLBACK', you can do any kind of `COMMIT' action with `LOCK TABLES'. To support `ROLLBACK' with the above table types, *MySQL* would have to be changed to store all old records that were updated and revert everything back to the starting point if `ROLLBACK' was issued. For simple cases, this isn't that hard to do (the current `isamlog' could be used for this purpose), but it would be much more difficult to implement `ROLLBACK' for `ALTER/DROP/CREATE TABLE'. To avoid using `ROLLBACK', you can use the following strategy: 1. Use `LOCK TABLES ...' to lock all the tables you want to access. 2. Test conditions. 3. Update if everything is okay. 4. Use `UNLOCK TABLES' to release your locks. This is usually a much faster method than using transactions with possible `ROLLBACK's, although not always. The only situation this solution doesn't handle is when someone kills the threads in the middle of an update. In this case, all locks will be released but some of the updates may not have been executed. You can also use functions to update records in a single operation. You can get a very efficient application by using the following techniques: * Modify fields relative to their current value. * Update only those fields that actually have changed. For example, when we are doing updates to some customer information, we update only the customer data that has changed and test only that none of the changed data, or data that depend on the changed data, has changed compared to the original row. The test for changed data is done with the `WHERE' clause in the `UPDATE' statement. If the record wasn't updated, we give the client a message: "Some of the data you have changed have been changed by another user". Then we show the old row versus the new row in a window, so the user can decide which version of the customer record he should use. This gives us something that is similar to column locking but is actually even better, because we only update some of the columns, using values that are relative to their current values. This means that typical `UPDATE' statements look something like these: UPDATE tablename SET pay_back=pay_back+'relative change'; UPDATE customer SET customer_date='current_date', address='new address', phone='new phone', money_he_owes_us=money_he_owes_us+'new_money' WHERE customer_id=id AND address='old address' AND phone='old phone'; As you can see, this is very efficient and works even if another client has changed the values in the `pay_back' or `money_he_owes_us' columns. In many cases, users have wanted `ROLLBACK' and/or `LOCK TABLES' for the purpose of managing unique identifiers for some tables. This can be handled much more efficiently by using an `AUTO_INCREMENT' column and either the SQL function `LAST_INSERT_ID()' or the C API function `mysql_insert_id()'. *Note `mysql_insert_id()': mysql_insert_id. At *MySQL AB*, we have never had any need for row-level locking because we have always been able to code around it. Some cases really need row locking, but they are very few. If you want row-level locking, you can use a flag column in the table and do something like this: UPDATE tbl_name SET row_flag=1 WHERE id=ID; *MySQL* returns 1 for the number of affected rows if the row was found and `row_flag' wasn't already 1 in the original row. You can think of it as *MySQL* changed the above query to: UPDATE tbl_name SET row_flag=1 WHERE id=ID and row_flag <> 1; The MySQL Access Privilege System ********************************* *MySQL* has an advanced but non-standard security/privilege system. This section describes how it works. General Security ================ Anyone using *MySQL* on a computer connected to the Internet should read this section to avoid the most common security mistakes. In discussing security, we emphasize the necessity of fully protecting the entire server host (not simply the *MySQL* server) against all types of applicable attacks: eavesdropping, altering, playback, and denial of service. We do not cover all aspects of availability and fault tolerance here. *MySQL* uses security based on Access Control Lists (ACLs) for all connections, queries, and other operations that a user may attempt to perform. There is also some support for SSL-encrypted connections between *MySQL* clients and servers. Many of the concepts discussed here are not specific to *MySQL* at all; the same general ideas apply to almost all applications. When running *MySQL*, follow these guidelines whenever possible: * DON'T EVER GIVE ANYONE (EXCEPT THE *MySQL* ROOT USER) ACCESS TO THE `user' TABLE IN THE `mysql' DATABASE! The encrypted password is the real password in *MySQL*. If you know the password listed in the `user' table for a given user, you can easily log in as that user if you have access to the host listed for that account. * Learn the *MySQL* access privilege system. The `GRANT' and `REVOKE' commands are used for controlling access to *MySQL*. Do not grant any more privileges than necessary. Never grant privileges to all hosts. Checklist: - Try `mysql -u root'. If you are able to connect successfully to the server without being asked for a password, you have problems. Anyone can connect to your *MySQL* server as the *MySQL* `root' user with full privileges! Review the *MySQL* installation instructions, paying particular attention to the item about setting a `root' password. - Use the command `SHOW GRANTS' and check to see who has access to what. Remove those privileges that are not necessary using the `REVOKE' command. * Do not keep any plain-text passwords in your database. When your computer becomes compromised, the intruder can take the full list of passwords and use them. Instead use `MD5()' or another one-way hashing function. * Do not choose passwords from dictionaries. There are special programs to break them. Even passwords like "xfish98" are very bad. Much better is "duag98" which contains the same word "fish" but typed one key to the left on a standard QWERTY keyboard. Another method is to use "Mhall" which is taken from the first characters of each word in the sentence "Mary had a little lamb." This is easy to remember and type, but difficult to guess for someone who does not know it. * Invest in a firewall. This protects you from at least 50% of all types of exploits in any software. Put *MySQL* behind the firewall or in a demilitarized zone (DMZ). Checklist: - Try to scan your ports from the Internet using a tool such as `nmap'. *MySQL* uses port 3306 by default. This port should be inaccessible from untrusted hosts. Another simple way to check whether or not your *MySQL* port is open is to try the following command from some remote machine, where `server_host' is the hostname of your *MySQL* server: shell> telnet server_host 3306 If you get a connection and some garbage characters, the port is open, and should be closed on your firewall or router, unless you really have a good reason to keep it open. If `telnet' just hangs or the connection is refused, everything is OK; the port is blocked. * Do not trust any data entered by your users. They can try to trick your code by entering special or escaped character sequences in Web forms, URLs, or whatever application you have built. Be sure that your application remains secure if a user enters something like "`; DROP DATABASE mysql;'". This is an extreme example, but large security leaks and data loss may occur as a result of hackers using similar techniques, if you do not prepare for them. Also remember to check numeric data. A common mistake is to protect only strings. Sometimes people think that if a database contains only publicly available data that it need not be protected. This is incorrect. At least denial-of-service type attacks can be performed on such databases. The simplest way to protect from this type of attack is to use apostrophes around the numeric constants: `SELECT * FROM table WHERE ID='234'' rather than `SELECT * FROM table WHERE ID=234'. *MySQL* automatically converts this string to a number and strips all non-numeric symbols from it. Checklist: - All Web applications: * Try to enter `'' and `"' in all your Web forms. If you get any kind of *MySQL* error, investigate the problem right away. * Try to modify any dynamic URLs by adding `%22' (`"'), `%23' (`#'), and `%27' (`'') in the URL. * Try to modify datatypes in dynamic URLs from numeric ones to character ones containing characters from previous examples. Your application should be safe against this and similar attacks. * Try to enter characters, spaces, and special symbols instead of numbers in numeric fields. Your application should remove them before passing them to *MySQL* or your application should generate an error. Passing unchecked values to *MySQL* is very dangerous! * Check data sizes before passing them to *MySQL*. * Consider having your application connect to the database using a different user name than the one you use for administrative purposes. Do not give your applications any more access privileges than they need. - Users of PHP: * Check out the `addslashes()' function. As of PHP 4.0.3, a `mysql_escape_string()' function is available that is based on the function of the same name in the *MySQL* C API. - Users of *MySQL* C API: * Check out the `mysql_escape_string()' API call. - Users of *MySQL*++: * Check out the `escape' and `quote' modifiers for query streams. - Users of Perl DBI: * Check out the `quote()' method or use placeholders. - Users of Java JDBC: * Use a `PreparedStatement' object and placeholders. * Do not transmit plain (unencrypted) data over the Internet. These data are accessible to everyone who has the time and ability to intercept it and use it for their own purposes. Instead, use an encrypted protocol such as SSL or SSH. *MySQL* supports internal SSL connections as of Version 3.23.9. SSH port-forwarding can be used to create an encrypted (and compressed) tunnel for the communication. * Learn to use the `tcpdump' and `strings' utilities. For most cases, you can check whether or not *MySQL* data streams are unencrypted by issuing a command like the following: shell> tcpdump -l -i eth0 -w - src or dst port 3306 | strings (This works under Linux and should work with small modifications under other systems). Warning: If you do not see data this doesn't always actually mean that it is encrypted. If you need high security, you should consult with a security expert. How to Make MySQL Secure Against Crackers ========================================= When you connect to a *MySQL* server, you normally should use a password. The password is not transmitted in clear text over the connection, however the encryption algorithm is not very strong, and with some effort a clever attacker can crack the password if he is able to sniff the traffic between the client and the server. If the connection between the client and the server goes through an untrusted network, you should use an SSH tunnel to encrypt the communication. All other information is transferred as text that can be read by anyone who is able to watch the connection. If you are concerned about this, you can use the compressed protocol (in *MySQL* Version 3.22 and above) to make things much harder. To make things even more secure you should use `ssh'. You can find an open source `ssh' client at `http://www.openssh.org', and a commercial `ssh' client at `http://www.ssh.com'. With this, you can get an encrypted TCP/IP connection between a *MySQL* server and a *MySQL* client. To make a *MySQL* system secure, you should strongly consider the following suggestions: * Use passwords for all *MySQL* users. Remember that anyone can log in as any other person as simply as `mysql -u other_user db_name' if `other_user' has no password. It is common behavior with client/server applications that the client may specify any user name. You can change the password of all users by editing the `mysql_install_db' script before you run it, or only the password for the *MySQL* `root' user like this: shell> mysql -u root mysql mysql> UPDATE user SET Password=PASSWORD('new_password') WHERE user='root'; mysql> FLUSH PRIVILEGES; * Don't run the *MySQL* daemon as the Unix `root' user. This is very dangerous, because any user with `FILE' privileges will be able to create files as `root' (for example, `~root/.bashrc'). To prevent this, `mysqld' will refuse to run as `root' unless it is specified directly using a `--user=root' option. `mysqld' can be run as an ordinary unprivileged user instead. You can also create a new Unix user `mysql' to make everything even more secure. If you run `mysqld' as another Unix user, you don't need to change the `root' user name in the `user' table, because *MySQL* user names have nothing to do with Unix user names. To start `mysqld' as another Unix user, add a `user' line that specifies the user name to the `[mysqld]' group of the `/etc/my.cnf' option file or the `my.cnf' option file in the server's data directory. For example: [mysqld] user=mysql This will cause the server to start as the designated user whether you start it manually or by using `safe_mysqld' or `mysql.server'. For more details, see *Note Changing *MySQL* user: Changing MySQL user. * Don't support symlinks to tables (This can be disabled with the `--skip-symlink' option. This is especially important if you run `mysqld' as root as anyone that has write access to the mysqld data directories could then delete any file in the system! *Note Symbolic links to tables::. * Check that the Unix user that `mysqld' runs as is the only user with read/write privileges in the database directories. * Don't give the *process* privilege to all users. The output of `mysqladmin processlist' shows the text of the currently executing queries, so any user who is allowed to execute that command might be able to see if another user issues an `UPDATE user SET password=PASSWORD('not_secure')' query. `mysqld' reserves an extra connection for users who have the *process* privilege, so that a *MySQL* `root' user can log in and check things even if all normal connections are in use. * Don't give the *file* privilege to all users. Any user that has this privilege can write a file anywhere in the file system with the privileges of the `mysqld' daemon! To make this a bit safer, all files generated with `SELECT ... INTO OUTFILE' are readable to everyone, and you cannot overwrite existing files. The *file* privilege may also be used to read any file accessible to the Unix user that the server runs as. This could be abused, for example, by using `LOAD DATA' to load `/etc/passwd' into a table, which can then be read with `SELECT'. * If you don't trust your DNS, you should use IP numbers instead of hostnames in the grant tables. In principle, the `--secure' option to `mysqld' should make hostnames safe. In any case, you should be very careful about creating grant table entries using hostname values that contain wild cards! * If you want to restrict the number of connections for a single user, you can do this by setting the `max_user_connections' variable in `mysqld'. Startup Options for `mysqld' Concerning Security ================================================ The following `mysqld' options affect networking security: `--secure' IP numbers returned by the `gethostbyname()' system call are checked to make sure they resolve back to the original hostname. This makes it harder for someone on the outside to get access by pretending to be another host. This option also adds some sanity checks of hostnames. The option is turned off by default in *MySQL* Version 3.21 because sometimes it takes a long time to perform backward resolutions. *MySQL* Version 3.22 caches hostnames and has this option enabled by default. `--skip-grant-tables' This option causes the server not to use the privilege system at all. This gives everyone _full access_ to all databases! (You can tell a running server to start using the grant tables again by executing `mysqladmin flush-privileges' or `mysqladmin reload'.) `--skip-name-resolve' Hostnames are not resolved. All `Host' column values in the grant tables must be IP numbers or `localhost'. `--skip-networking' Don't allow TCP/IP connections over the network. All connections to `mysqld' must be made via Unix sockets. This option is unsuitable for systems that use MIT-pthreads, because the MIT-pthreads package doesn't support Unix sockets. `--skip-show-database' With this option, the `SHOW DATABASES' statement doesn't return anything. `--safe-show-database' With this option, `SHOW DATABASES' returns only those databases for which the user has some kind of privilege. What the Privilege System Does ============================== The primary function of the *MySQL* privilege system is to authenticate a user connecting from a given host, and to associate that user with privileges on a database such as *select*, *insert*, *update* and *delete*. Additional functionality includes the ability to have an anonymous user and to grant privileges for *MySQL*-specific functions such as `LOAD DATA INFILE' and administrative operations. MySQL User Names and Passwords ============================== There are several distinctions between the way user names and passwords are used by *MySQL* and the way they are used by Unix or Windows: * User names, as used by *MySQL* for authentication purposes, have nothing to do with Unix user names (login names) or Windows user names. Most *MySQL* clients by default try to log in using the current Unix user name as the *MySQL* user name, but that is for convenience only. Client programs allow a different name to be specified with the `-u' or `--user' options. This means that you can't make a database secure in any way unless all *MySQL* user names have passwords. Anyone may attempt to connect to the server using any name, and they will succeed if they specify any name that doesn't have a password. * *MySQL* user names can be up to 16 characters long; Unix user names typically are limited to 8 characters. * *MySQL* passwords have nothing to do with Unix passwords. There is no necessary connection between the password you use to log in to a Unix machine and the password you use to access a database on that machine. * *MySQL* encrypts passwords using a different algorithm than the one used during the Unix login process. See the descriptions of the `PASSWORD()' and `ENCRYPT()' functions in *Note Miscellaneous functions::. Note that even if the password is stored 'scrambled', and knowing your 'scrambled' password is enough to be able to connect to the *MySQL* server! *MySQL* users and they privileges are normally created with the `GRANT' command. *Note GRANT::. When you login to a *MySQL* server with a command line client you should specify the password with `--password=your-password'. *Note Connecting::. mysql --user=monty --password=guess database_name If you want the client to prompt for a password, you should use `--password' without any argument mysql --user=monty --password database_name or the short form: mysql -u monty -p database_name Note that in the last example the password is *NOT* 'database_name'. If you want to use the -p option to supply a password you should do like this: mysql -u monty -pguess database_name On some system the library call that *MySQL* uses to prompt for a password will automaticly cut the password to 8 characters. Internally *MySQL* doesn't have any limit for the length of the password. Connecting to the MySQL Server ============================== *MySQL* client programs generally require that you specify connection parameters when you want to access a *MySQL* server: the host you want to connect to, your user name, and your password. For example, the `mysql' client can be started like this (optional arguments are enclosed between `[' and `]'): shell> mysql [-h host_name] [-u user_name] [-pyour_pass] Alternate forms of the `-h', `-u', and `-p' options are `--host=host_name', `--user=user_name', and `--password=your_pass'. Note that there is _no space_ between `-p' or `--password=' and the password following it. *NOTE:* Specifying a password on the command line is not secure! Any user on your system may then find out your password by typing a command like: `ps auxww'. *Note Option files::. `mysql' uses default values for connection parameters that are missing from the command line: * The default hostname is `localhost'. * The default user name is your Unix login name. * No password is supplied if `-p' is missing. Thus, for a Unix user `joe', the following commands are equivalent: shell> mysql -h localhost -u joe shell> mysql -h localhost shell> mysql -u joe shell> mysql Other *MySQL* clients behave similarly. On Unix systems, you can specify different default values to be used when you make a connection, so that you need not enter them on the command line each time you invoke a client program. This can be done in a couple of ways: * You can specify connection parameters in the `[client]' section of the `.my.cnf' configuration file in your home directory. The relevant section of the file might look like this: [client] host=host_name user=user_name password=your_pass *Note Option files::. * You can specify connection parameters using environment variables. The host can be specified for `mysql' using `MYSQL_HOST'. The *MySQL* user name can be specified using `USER' (this is for Windows only). The password can be specified using `MYSQL_PWD' (but this is insecure; see the next section). *Note Environment variables::. Keeping Your Password Secure ============================ It is inadvisable to specify your password in a way that exposes it to discovery by other users. The methods you can use to specify your password when you run client programs are listed below, along with an assessment of the risks of each method: * Never give a normal user access to the `mysql.user' table. Knowing the encrypted password for a user makes it possible to login as this user. The passwords are only scrambled so that one shouldn't be able to see the real password you used (if you happen to use a similar password with your other applications). * Use a `-pyour_pass' or `--password=your_pass' option on the command line. This is convenient but insecure, because your password becomes visible to system status programs (such as `ps') that may be invoked by other users to display command lines. (*MySQL* clients typically overwrite the command-line argument with zeroes during their initialization sequence, but there is still a brief interval during which the value is visible.) * Use a `-p' or `--password' option (with no `your_pass' value specified). In this case, the client program solicits the password from the terminal: shell> mysql -u user_name -p Enter password: ******** The `*' characters represent your password. It is more secure to enter your password this way than to specify it on the command line because it is not visible to other users. However, this method of entering a password is suitable only for programs that you run interactively. If you want to invoke a client from a script that runs non-interactively, there is no opportunity to enter the password from the terminal. On some systems, you may even find that the first line of your script is read and interpreted (incorrectly) as your password! * Store your password in a configuration file. For example, you can list your password in the `[client]' section of the `.my.cnf' file in your home directory: [client] password=your_pass If you store your password in `.my.cnf', the file should not be group or world readable or writable. Make sure the file's access mode is `400' or `600'. *Note Option files::. * You can store your password in the `MYSQL_PWD' environment variable, but this method must be considered extremely insecure and should not be used. Some versions of `ps' include an option to display the environment of running processes; your password will be in plain sight for all to see if you set `MYSQL_PWD'. Even on systems without such a version of `ps', it is unwise to assume there is no other method to observe process environments. *Note Environment variables::. All in all, the safest methods are to have the client program prompt for the password or to specify the password in a properly protected `.my.cnf' file. Privileges Provided by MySQL ============================ Information about user privileges is stored in the `user', `db', `host', `tables_priv', and `columns_priv' tables in the `mysql' database (that is, in the database named `mysql'). The *MySQL* server reads the contents of these tables when it starts up and under the circumstances indicated in *Note Privilege changes::. The names used in this manual to refer to the privileges provided by *MySQL* are shown below, along with the table column name associated with each privilege in the grant tables and the context in which the privilege applies: *Privilege* *Column* *Context* *select* `Select_priv' tables *insert* `Insert_priv' tables *update* `Update_priv' tables *delete* `Delete_priv' tables *index* `Index_priv' tables *alter* `Alter_priv' tables *create* `Create_priv' databases, tables, or indexes *drop* `Drop_priv' databases or tables *grant* `Grant_priv' databases or tables *references*`References_priv' databases or tables *reload* `Reload_priv' server administration *shutdown* `Shutdown_priv' server administration *process* `Process_priv' server administration *file* `File_priv' file access on server The *select*, *insert*, *update*, and *delete* privileges allow you to perform operations on rows in existing tables in a database. `SELECT' statements require the *select* privilege only if they actually retrieve rows from a table. You can execute certain `SELECT' statements even without permission to access any of the databases on the server. For example, you could use the `mysql' client as a simple calculator: mysql> SELECT 1+1; mysql> SELECT PI()*2; The *index* privilege allows you to create or drop (remove) indexes. The *alter* privilege allows you to use `ALTER TABLE'. The *create* and *drop* privileges allow you to create new databases and tables, or to drop (remove) existing databases and tables. Note that if you grant the *drop* privilege for the `mysql' database to a user, that user can drop the database in which the *MySQL* access privileges are stored! The *grant* privilege allows you to give to other users those privileges you yourself possess. The *file* privilege gives you permission to read and write files on the server using the `LOAD DATA INFILE' and `SELECT ... INTO OUTFILE' statements. Any user to whom this privilege is granted can read or write any file that the *MySQL* server can read or write. The remaining privileges are used for administrative operations, which are performed using the `mysqladmin' program. The table below shows which `mysqladmin' commands each administrative privilege allows you to execute: *Privilege* *Commands permitted to privilege holders* *reload* `reload', `refresh', `flush-privileges', `flush-hosts', `flush-logs', and `flush-tables' *shutdown* `shutdown' *process* `processlist', `kill' The `reload' command tells the server to re-read the grant tables. The `refresh' command flushes all tables and opens and closes the log files. `flush-privileges' is a synonym for `reload'. The other `flush-*' commands perform functions similar to `refresh' but are more limited in scope, and may be preferable in some instances. For example, if you want to flush just the log files, `flush-logs' is a better choice than `refresh'. The `shutdown' command shuts down the server. The `processlist' command displays information about the threads executing within the server. The `kill' command kills server threads. You can always display or kill your own threads, but you need the *process* privilege to display or kill threads initiated by other users. *Note KILL::. It is a good idea in general to grant privileges only to those users who need them, but you should exercise particular caution in granting certain privileges: * The *grant* privilege allows users to give away their privileges to other users. Two users with different privileges and with the *grant* privilege are able to combine privileges. * The *alter* privilege may be used to subvert the privilege system by renaming tables. * The *file* privilege can be abused to read any world-readable file on the server into a database table, the contents of which can then be accessed using `SELECT'. This includes the contents of all databases hosted by the server! * The *shutdown* privilege can be abused to deny service to other users entirely, by terminating the server. * The *process* privilege can be used to view the plain text of currently executing queries, including queries that set or change passwords. * Privileges on the `mysql' database can be used to change passwords and other access privilege information. (Passwords are stored encrypted, so a malicious user cannot simply read them to know the plain text password). If they can access the `mysql.user' password column, they can use it to log into the *MySQL* server for the given user. (With sufficient privileges, the same user can replace a password with a different one.) There are some things that you cannot do with the *MySQL* privilege system: * You cannot explicitly specify that a given user should be denied access. That is, you cannot explicitly match a user and then refuse the connection. * You cannot specify that a user has privileges to create or drop tables in a database but not to create or drop the database itself. How the Privilege System Works ============================== The *MySQL* privilege system ensures that all users may do exactly the things that they are supposed to be allowed to do. When you connect to a *MySQL* server, your identity is determined by *the host from which you connect* and *the user name you specify*. The system grants privileges according to your identity and *what you want to do*. *MySQL* considers both your hostname and user name in identifying you because there is little reason to assume that a given user name belongs to the same person everywhere on the Internet. For example, the user `bill' who connects from `whitehouse.gov' need not be the same person as the user `bill' who connects from `microsoft.com'. *MySQL* handles this by allowing you to distinguish users on different hosts that happen to have the same name: you can grant `bill' one set of privileges for connections from `whitehouse.gov', and a different set of privileges for connections from `microsoft.com'. *MySQL* access control involves two stages: * Stage 1: The server checks whether or not you are even allowed to connect. * Stage 2: Assuming you can connect, the server checks each request you issue to see whether or not you have sufficient privileges to perform it. For example, if you try to select rows from a table in a database or drop a table from the database, the server makes sure you have the *select* privilege for the table or the *drop* privilege for the database. The server uses the `user', `db', and `host' tables in the `mysql' database at both stages of access control. The fields in these grant tables are shown below: *Table name* `user' `db' `host' *Scope `Host' `Host' `Host' fields* `User' `Db' `Db' `Password' `User' *Privilege `Select_priv' `Select_priv' `Select_priv' fields* `Insert_priv' `Insert_priv' `Insert_priv' `Update_priv' `Update_priv' `Update_priv' `Delete_priv' `Delete_priv' `Delete_priv' `Index_priv' `Index_priv' `Index_priv' `Alter_priv' `Alter_priv' `Alter_priv' `Create_priv' `Create_priv' `Create_priv' `Drop_priv' `Drop_priv' `Drop_priv' `Grant_priv' `Grant_priv' `Grant_priv' `References_priv' `Reload_priv' `Shutdown_priv' `Process_priv' `File_priv' For the second stage of access control (request verification), the server may, if the request involves tables, additionally consult the `tables_priv' and `columns_priv' tables. The fields in these tables are shown below: *Table name* `tables_priv' `columns_priv' *Scope `Host' `Host' fields* `Db' `Db' `User' `User' `Table_name' `Table_name' `Column_name' *Privilege `Table_priv' `Column_priv' fields* `Column_priv' *Other `Timestamp' `Timestamp' fields* `Grantor' Each grant table contains scope fields and privilege fields. Scope fields determine the scope of each entry in the tables, that is, the context in which the entry applies. For example, a `user' table entry with `Host' and `User' values of `'thomas.loc.gov'' and `'bob'' would be used for authenticating connections made to the server by `bob' from the host `thomas.loc.gov'. Similarly, a `db' table entry with `Host', `User', and `Db' fields of `'thomas.loc.gov'', `'bob'' and `'reports'' would be used when `bob' connects from the host `thomas.loc.gov' to access the `reports' database. The `tables_priv' and `columns_priv' tables contain scope fields indicating tables or table/column combinations to which each entry applies. For access-checking purposes, comparisons of `Host' values are case insensitive. `User', `Password', `Db', and `Table_name' values are case sensitive. `Column_name' values are case insensitive in *MySQL* Version 3.22.12 or later. Privilege fields indicate the privileges granted by a table entry, that is, what operations can be performed. The server combines the information in the various grant tables to form a complete description of a user's privileges. The rules used to do this are described in *Note Request access::. Scope fields are strings, declared as shown below; the default value for each is the empty string: *Field *Type* name* `Host' `CHAR(60)' `User' `CHAR(16)' `Password' `CHAR(16)' `Db' `CHAR(64)' (`CHAR(60)' for the `tables_priv' and `columns_priv' tables) `Table_name'`CHAR(60)' `Column_name'`CHAR(60)' In the `user', `db' and `host' tables, all privilege fields are declared as `ENUM('N','Y')' -- each can have a value of `'N'' or `'Y'', and the default value is `'N''. In the `tables_priv' and `columns_priv' tables, the privilege fields are declared as `SET' fields: *Table name* *Field name* *Possible set elements* `tables_priv' `Table_priv' `'Select', 'Insert', 'Update', 'Delete', 'Create', 'Drop', 'Grant', 'References', 'Index', 'Alter'' `tables_priv' `Column_priv' `'Select', 'Insert', 'Update', 'References'' `columns_priv' `Column_priv' `'Select', 'Insert', 'Update', 'References'' Briefly, the server uses the grant tables like this: * The `user' table scope fields determine whether to allow or reject incoming connections. For allowed connections, any privileges granted in the `user' table indicate the user's global (superuser) privileges. These privileges apply to *all* databases on the server. * The `db' and `host' tables are used together: - The `db' table scope fields determine which users can access which databases from which hosts. The privilege fields determine which operations are allowed. - The `host' table is used as an extension of the `db' table when you want a given `db' table entry to apply to several hosts. For example, if you want a user to be able to use a database from several hosts in your network, leave the `Host' value empty in the user's `db' table entry, then populate the `host' table with an entry for each of those hosts. This mechanism is described more detail in *Note Request access::. * The `tables_priv' and `columns_priv' tables are similar to the `db' table, but are more fine-grained: they apply at the table and column levels rather than at the database level. Note that administrative privileges (*reload*, *shutdown*, etc.) are specified only in the `user' table. This is because administrative operations are operations on the server itself and are not database-specific, so there is no reason to list such privileges in the other grant tables. In fact, only the `user' table need be consulted to determine whether or not you can perform an administrative operation. The *file* privilege is specified only in the `user' table, too. It is not an administrative privilege as such, but your ability to read or write files on the server host is independent of the database you are accessing. The `mysqld' server reads the contents of the grant tables once, when it starts up. Changes to the grant tables take effect as indicated in *Note Privilege changes::. When you modify the contents of the grant tables, it is a good idea to make sure that your changes set up privileges the way you want. For help in diagnosing problems, see *Note Access denied::. For advice on security issues, *note Security::. A useful diagnostic tool is the `mysqlaccess' script, which Yves Carlier has provided for the *MySQL* distribution. Invoke `mysqlaccess' with the `--help' option to find out how it works. Note that `mysqlaccess' checks access using only the `user', `db' and `host' tables. It does not check table- or column-level privileges. Access Control, Stage 1: Connection Verification ================================================ When you attempt to connect to a *MySQL* server, the server accepts or rejects the connection based on your identity and whether or not you can verify your identity by supplying the correct password. If not, the server denies access to you completely. Otherwise, the server accepts the connection, then enters Stage 2 and waits for requests. Your identity is based on two pieces of information: * The host from which you connect * Your *MySQL* user name Identity checking is performed using the three `user' table scope fields (`Host', `User', and `Password'). The server accepts the connection only if a `user' table entry matches your hostname and user name, and you supply the correct password. Values in the `user' table scope fields may be specified as follows: * A `Host' value may be a hostname or an IP number, or `'localhost'' to indicate the local host. * You can use the wild-card characters `%' and `_' in the `Host' field. * A `Host' value of `'%'' matches any hostname. * A blank `Host' value means that the privilege should be anded with the entry in the `host' table that matches the given host name. You can find more information about this in the next chapter. * As of *MySQL* Version 3.23, for `Host' values specified as IP numbers, you can specify a netmask indicating how many address bits to use for the network number. For example: GRANT ALL PRIVILEGES on db.* to david@'192.58.197.0/255.255.255.0'; This will allow everyone to connect from an IP where the following is true: user_ip & netmask = host_ip. In the above example all IP:s in the interval 192.58.197.0 - 192.58.197.255 can connect to the *MySQL* server. * Wild-card characters are not allowed in the `User' field, but you can specify a blank value, which matches any name. If the `user' table entry that matches an incoming connection has a blank user name, the user is considered to be the anonymous user (the user with no name), rather than the name that the client actually specified. This means that a blank user name is used for all further access checking for the duration of the connection (that is, during Stage 2). * The `Password' field can be blank. This does not mean that any password matches, it means the user must connect without specifying a password. Non-blank `Password' values represent encrypted passwords. *MySQL* does not store passwords in plaintext form for anyone to see. Rather, the password supplied by a user who is attempting to connect is encrypted (using the `PASSWORD()' function). The encrypted password is then used when the client/server is checking if the password is correct (This is done without the encrypted password ever traveling over the connection.) Note that from *MySQL*'s point of view the encrypted password is the REAL password, so you should not give anyone access to it! In particular, don't give normal users read access to the tables in the `mysql' database! The examples below show how various combinations of `Host' and `User' values in `user' table entries apply to incoming connections: `Host' *value* `User' *Connections matched by entry* *value* `'thomas.loc.gov'' `'fred'' `fred', connecting from `thomas.loc.gov' `'thomas.loc.gov'' `''' Any user, connecting from `thomas.loc.gov' `'%'' `'fred'' `fred', connecting from any host `'%'' `''' Any user, connecting from any host `'%.loc.gov'' `'fred'' `fred', connecting from any host in the `loc.gov' domain `'x.y.%'' `'fred'' `fred', connecting from `x.y.net', `x.y.com',`x.y.edu', etc. (this is probably not useful) `'144.155.166.177''`'fred'' `fred', connecting from the host with IP address `144.155.166.177' `'144.155.166.%'' `'fred'' `fred', connecting from any host in the `144.155.166' class C subnet `'144.155.166.0/255.255.255.0''`'fred'' Same as previous example Because you can use IP wild-card values in the `Host' field (for example, `'144.155.166.%'' to match every host on a subnet), there is the possibility that someone might try to exploit this capability by naming a host `144.155.166.somewhere.com'. To foil such attempts, *MySQL* disallows matching on hostnames that start with digits and a dot. Thus, if you have a host named something like `1.2.foo.com', its name will never match the `Host' column of the grant tables. Only an IP number can match an IP wild-card value. An incoming connection may be matched by more than one entry in the `user' table. For example, a connection from `thomas.loc.gov' by `fred' would be matched by several of the entries just shown above. How does the server choose which entry to use if more than one matches? The server resolves this question by sorting the `user' table after reading it at startup time, then looking through the entries in sorted order when a user attempts to connect. The first matching entry is the one that is used. `user' table sorting works as follows. Suppose the `user' table looks like this: +-----------+----------+- | Host | User | ... +-----------+----------+- | % | root | ... | % | jeffrey | ... | localhost | root | ... | localhost | | ... +-----------+----------+- When the server reads in the table, it orders the entries with the most-specific `Host' values first (`'%'' in the `Host' column means "any host" and is least specific). Entries with the same `Host' value are ordered with the most-specific `User' values first (a blank `User' value means "any user" and is least specific). The resulting sorted `user' table looks like this: +-----------+----------+- | Host | User | ... +-----------+----------+- | localhost | root | ... | localhost | | ... | % | jeffrey | ... | % | root | ... +-----------+----------+- When a connection is attempted, the server looks through the sorted entries and uses the first match found. For a connection from `localhost' by `jeffrey', the entries with `'localhost'' in the `Host' column match first. Of those, the entry with the blank user name matches both the connecting hostname and user name. (The `'%'/'jeffrey'' entry would have matched, too, but it is not the first match in the table.) Here is another example. Suppose the `user' table looks like this: +----------------+----------+- | Host | User | ... +----------------+----------+- | % | jeffrey | ... | thomas.loc.gov | | ... +----------------+----------+- The sorted table looks like this: +----------------+----------+- | Host | User | ... +----------------+----------+- | thomas.loc.gov | | ... | % | jeffrey | ... +----------------+----------+- A connection from `thomas.loc.gov' by `jeffrey' is matched by the first entry, whereas a connection from `whitehouse.gov' by `jeffrey' is matched by the second. A common misconception is to think that for a given user name, all entries that explicitly name that user will be used first when the server attempts to find a match for the connection. This is simply not true. The previous example illustrates this, where a connection from `thomas.loc.gov' by `jeffrey' is first matched not by the entry containing `'jeffrey'' as the `User' field value, but by the entry with no user name! If you have problems connecting to the server, print out the `user' table and sort it by hand to see where the first match is being made. Access Control, Stage 2: Request Verification ============================================= Once you establish a connection, the server enters Stage 2. For each request that comes in on the connection, the server checks whether you have sufficient privileges to perform it, based on the type of operation you wish to perform. This is where the privilege fields in the grant tables come into play. These privileges can come from any of the `user', `db', `host', `tables_priv', or `columns_priv' tables. The grant tables are manipulated with `GRANT' and `REVOKE' commands. *Note `GRANT': GRANT. (You may find it helpful to refer to *Note Privileges::, which lists the fields present in each of the grant tables.) The `user' table grants privileges that are assigned to you on a global basis and that apply no matter what the current database is. For example, if the `user' table grants you the *delete* privilege, you can delete rows from any database on the server host! In other words, `user' table privileges are superuser privileges. It is wise to grant privileges in the `user' table only to superusers such as server or database administrators. For other users, you should leave the privileges in the `user' table set to `'N'' and grant privileges on a database-specific basis only, using the `db' and `host' tables. The `db' and `host' tables grant database-specific privileges. Values in the scope fields may be specified as follows: * The wild-card characters `%' and `_' can be used in the `Host' and `Db' fields of either table. * A `'%'' `Host' value in the `db' table means "any host." A blank `Host' value in the `db' table means "consult the `host' table for further information." * A `'%'' or blank `Host' value in the `host' table means "any host." * A `'%'' or blank `Db' value in either table means "any database." * A blank `User' value in either table matches the anonymous user. The `db' and `host' tables are read in and sorted when the server starts up (at the same time that it reads the `user' table). The `db' table is sorted on the `Host', `Db', and `User' scope fields, and the `host' table is sorted on the `Host' and `Db' scope fields. As with the `user' table, sorting puts the most-specific values first and least-specific values last, and when the server looks for matching entries, it uses the first match that it finds. The `tables_priv' and `columns_priv' tables grant table- and column-specific privileges. Values in the scope fields may be specified as follows: * The wild-card characters `%' and `_' can be used in the `Host' field of either table. * A `'%'' or blank `Host' value in either table means "any host." * The `Db', `Table_name' and `Column_name' fields cannot contain wild cards or be blank in either table. The `tables_priv' and `columns_priv' tables are sorted on the `Host', `Db', and `User' fields. This is similar to `db' table sorting, although the sorting is simpler because only the `Host' field may contain wild cards. The request verification process is described below. (If you are familiar with the access-checking source code, you will notice that the description here differs slightly from the algorithm used in the code. The description is equivalent to what the code actually does; it differs only to make the explanation simpler.) For administrative requests (*shutdown*, *reload*, etc.), the server checks only the `user' table entry, because that is the only table that specifies administrative privileges. Access is granted if the entry allows the requested operation and denied otherwise. For example, if you want to execute `mysqladmin shutdown' but your `user' table entry doesn't grant the *shutdown* privilege to you, access is denied without even checking the `db' or `host' tables. (They contain no `Shutdown_priv' column, so there is no need to do so.) For database-related requests (*insert*, *update*, etc.), the server first checks the user's global (superuser) privileges by looking in the `user' table entry. If the entry allows the requested operation, access is granted. If the global privileges in the `user' table are insufficient, the server determines the user's database-specific privileges by checking the `db' and `host' tables: 1. The server looks in the `db' table for a match on the `Host', `Db', and `User' fields. The `Host' and `User' fields are matched to the connecting user's hostname and *MySQL* user name. The `Db' field is matched to the database the user wants to access. If there is no entry for the `Host' and `User', access is denied. 2. If there is a matching `db' table entry and its `Host' field is not blank, that entry defines the user's database-specific privileges. 3. If the matching `db' table entry's `Host' field is blank, it signifies that the `host' table enumerates which hosts should be allowed access to the database. In this case, a further lookup is done in the `host' table to find a match on the `Host' and `Db' fields. If no `host' table entry matches, access is denied. If there is a match, the user's database-specific privileges are computed as the intersection (_not_ the union!) of the privileges in the `db' and `host' table entries, that is, the privileges that are `'Y'' in both entries. (This way you can grant general privileges in the `db' table entry and then selectively restrict them on a host-by-host basis using the `host' table entries.) After determining the database-specific privileges granted by the `db' and `host' table entries, the server adds them to the global privileges granted by the `user' table. If the result allows the requested operation, access is granted. Otherwise, the server checks the user's table and column privileges in the `tables_priv' and `columns_priv' tables and adds those to the user's privileges. Access is allowed or denied based on the result. Expressed in boolean terms, the preceding description of how a user's privileges are calculated may be summarized like this: global privileges OR (database privileges AND host privileges) OR table privileges OR column privileges It may not be apparent why, if the global `user' entry privileges are initially found to be insufficient for the requested operation, the server adds those privileges to the database-, table-, and column-specific privileges later. The reason is that a request might require more than one type of privilege. For example, if you execute an `INSERT ... SELECT' statement, you need both *insert* and *select* privileges. Your privileges might be such that the `user' table entry grants one privilege and the `db' table entry grants the other. In this case, you have the necessary privileges to perform the request, but the server cannot tell that from either table by itself; the privileges granted by the entries in both tables must be combined. The `host' table can be used to maintain a list of secure servers. At TcX, the `host' table contains a list of all machines on the local network. These are granted all privileges. You can also use the `host' table to indicate hosts that are _not_ secure. Suppose you have a machine `public.your.domain' that is located in a public area that you do not consider secure. You can allow access to all hosts on your network except that machine by using `host' table entries like this: +--------------------+----+- | Host | Db | ... +--------------------+----+- | public.your.domain | % | ... (all privileges set to 'N') | %.your.domain | % | ... (all privileges set to 'Y') +--------------------+----+- Naturally, you should always test your entries in the grant tables (for example, using `mysqlaccess') to make sure your access privileges are actually set up the way you think they are. When Privilege Changes Take Effect ================================== When `mysqld' starts, all grant table contents are read into memory and become effective at that point. Modifications to the grant tables that you perform using `GRANT', `REVOKE', or `SET PASSWORD' are noticed by the server immediately. If you modify the grant tables manually (using `INSERT', `UPDATE', etc.), you should execute a `FLUSH PRIVILEGES' statement or run `mysqladmin flush-privileges' or `mysqladmin reload' to tell the server to reload the grant tables. Otherwise your changes will have _no effect_ until you restart the server. If you change the grant tables manually but forget to reload the privileges, you will be wondering why your changes don't seem to make any difference! When the server notices that the grant tables have been changed, existing client connections are affected as follows: * Table and column privilege changes take effect with the client's next request. * Database privilege changes take effect at the next `USE db_name' command. Global privilege changes and password changes take effect the next time the client connects. Setting Up the Initial MySQL Privileges ======================================= After installing *MySQL*, you set up the initial access privileges by running `scripts/mysql_install_db'. *Note Quick install::. The `mysql_install_db' script starts up the `mysqld' server, then initializes the grant tables to contain the following set of privileges: * The *MySQL* `root' user is created as a superuser who can do anything. Connections must be made from the local host. *NOTE:* The initial `root' password is empty, so anyone can connect as `root' _without a password_ and be granted all privileges. * An anonymous user is created that can do anything with databases that have a name of `'test'' or starting with `'test_''. Connections must be made from the local host. This means any local user can connect without a password and be treated as the anonymous user. * Other privileges are denied. For example, normal users can't use `mysqladmin shutdown' or `mysqladmin processlist'. *NOTE:* The default privileges are different for Windows. *Note Windows running::. Because your installation is initially wide open, one of the first things you should do is specify a password for the *MySQL* `root' user. You can do this as follows (note that you specify the password using the `PASSWORD()' function): shell> mysql -u root mysql mysql> UPDATE user SET Password=PASSWORD('new_password') WHERE user='root'; mysql> FLUSH PRIVILEGES; You can, in *MySQL* Version 3.22 and above, use the `SET PASSWORD' statement: shell> mysql -u root mysql mysql> SET PASSWORD FOR root=PASSWORD('new_password'); Another way to set the password is by using the `mysqladmin' command: shell> mysqladmin -u root password new_password Only users with write/update access to the `mysql' database can change the password for others users. All normal users (not anonymous ones) can only change their own password with either of the above commands or with `SET PASSWORD=PASSWORD('new password')'. Note that if you update the password in the `user' table directly using the first method, you must tell the server to re-read the grant tables (with `FLUSH PRIVILEGES'), because the change will go unnoticed otherwise. Once the `root' password has been set, thereafter you must supply that password when you connect to the server as `root'. You may wish to leave the `root' password blank so that you don't need to specify it while you perform additional setup or testing. However, be sure to set it before using your installation for any real production work. See the `scripts/mysql_install_db' script to see how it sets up the default privileges. You can use this as a basis to see how to add other users. If you want the initial privileges to be different than those just described above, you can modify `mysql_install_db' before you run it. To re-create the grant tables completely, remove all the `.frm', `.MYI', and `.MYD' files in the directory containing the `mysql' database. (This is the directory named `mysql' under the database directory, which is listed when you run `mysqld --help'.) Then run the `mysql_install_db' script, possibly after editing it first to have the privileges you want. *NOTE:* For *MySQL* versions older than Version 3.22.10, you should NOT delete the `.frm' files. If you accidentally do this, you should copy them back from your *MySQL* distribution before running `mysql_install_db'. Adding New Users to MySQL ========================= You can add users two different ways: by using `GRANT' statements or by manipulating the *MySQL* grant tables directly. The preferred method is to use `GRANT' statements, because they are more concise and less error-prone. *Note GRANT::. There is also a lot of contributed programs like `phpmyadmin' that can be used to create and administrate users. *Note Contrib::. The examples below show how to use the `mysql' client to set up new users. These examples assume that privileges are set up according to the defaults described in the previous section. This means that to make changes, you must be on the same machine where `mysqld' is running, you must connect as the *MySQL* `root' user, and the `root' user must have the *insert* privilege for the `mysql' database and the *reload* administrative privilege. Also, if you have changed the `root' user password, you must specify it for the `mysql' commands below. You can add new users by issuing `GRANT' statements: shell> mysql --user=root mysql mysql> GRANT ALL PRIVILEGES ON *.* TO monty@localhost IDENTIFIED BY 'some_pass' WITH GRANT OPTION; mysql> GRANT ALL PRIVILEGES ON *.* TO monty@"%" IDENTIFIED BY 'some_pass' WITH GRANT OPTION; mysql> GRANT RELOAD,PROCESS ON *.* TO admin@localhost; mysql> GRANT USAGE ON *.* TO dummy@localhost; These `GRANT' statements set up three new users: `monty' A full superuser who can connect to the server from anywhere, but who must use a password `'some_pass'' to do so. Note that we must issue `GRANT' statements for both `monty@localhost' and `monty@"%"'. If we don't add the entry with `localhost', the anonymous user entry for `localhost' that is created by `mysql_install_db' will take precedence when we connect from the local host, because it has a more specific `Host' field value and thus comes earlier in the `user' table sort order. `admin' A user who can connect from `localhost' without a password and who is granted the *reload* and *process* administrative privileges. This allows the user to execute the `mysqladmin reload', `mysqladmin refresh', and `mysqladmin flush-*' commands, as well as `mysqladmin processlist' . No database-related privileges are granted. (They can be granted later by issuing additional `GRANT' statements.) `dummy' A user who can connect without a password, but only from the local host. The global privileges are all set to `'N'' -- the `USAGE' privilege type allows you to create a user with no privileges. It is assumed that you will grant database-specific privileges later. You can also add the same user access information directly by issuing `INSERT' statements and then telling the server to reload the grant tables: shell> mysql --user=root mysql mysql> INSERT INTO user VALUES('localhost','monty',PASSWORD('some_pass'), 'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y'); mysql> INSERT INTO user VALUES('%','monty',PASSWORD('some_pass'), 'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y'); mysql> INSERT INTO user SET Host='localhost',User='admin', Reload_priv='Y', Process_priv='Y'; mysql> INSERT INTO user (Host,User,Password) VALUES('localhost','dummy',''); mysql> FLUSH PRIVILEGES; Depending on your *MySQL* version, you may have to use a different number of `'Y'' values above (versions prior to Version 3.22.11 had fewer privilege columns). For the `admin' user, the more readable extended `INSERT' syntax that is available starting with Version 3.22.11 is used. Note that to set up a superuser, you need only create a `user' table entry with the privilege fields set to `'Y''. No `db' or `host' table entries are necessary. The privilege columns in the `user' table were not set explicitly in the last `INSERT' statement (for the `dummy' user), so those columns are assigned the default value of `'N''. This is the same thing that `GRANT USAGE' does. The following example adds a user `custom' who can connect from hosts `localhost', `server.domain', and `whitehouse.gov'. He wants to access the `bankaccount' database only from `localhost', the `expenses' database only from `whitehouse.gov', and the `customer' database from all three hosts. He wants to use the password `stupid' from all three hosts. To set up this user's privileges using `GRANT' statements, run these commands: shell> mysql --user=root mysql mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP ON bankaccount.* TO custom@localhost IDENTIFIED BY 'stupid'; mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP ON expenses.* TO custom@whitehouse.gov IDENTIFIED BY 'stupid'; mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP ON customer.* TO custom@'%' IDENTIFIED BY 'stupid'; The reason that we do to grant statements for the user 'custom' is that we want the give the user access to *MySQL* both from the local machine with Unix sockets and from the remote machine 'whitehouse.gov' over TCP/IP. To set up the user's privileges by modifying the grant tables directly, run these commands (note the `FLUSH PRIVILEGES' at the end): shell> mysql --user=root mysql mysql> INSERT INTO user (Host,User,Password) VALUES('localhost','custom',PASSWORD('stupid')); mysql> INSERT INTO user (Host,User,Password) VALUES('server.domain','custom',PASSWORD('stupid')); mysql> INSERT INTO user (Host,User,Password) VALUES('whitehouse.gov','custom',PASSWORD('stupid')); mysql> INSERT INTO db (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv, Create_priv,Drop_priv) VALUES ('localhost','bankaccount','custom','Y','Y','Y','Y','Y','Y'); mysql> INSERT INTO db (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv, Create_priv,Drop_priv) VALUES ('whitehouse.gov','expenses','custom','Y','Y','Y','Y','Y','Y'); mysql> INSERT INTO db (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv, Create_priv,Drop_priv) VALUES('%','customer','custom','Y','Y','Y','Y','Y','Y'); mysql> FLUSH PRIVILEGES; The first three `INSERT' statements add `user' table entries that allow user `custom' to connect from the various hosts with the given password, but grant no permissions to him (all privileges are set to the default value of `'N''). The next three `INSERT' statements add `db' table entries that grant privileges to `custom' for the `bankaccount', `expenses', and `customer' databases, but only when accessed from the proper hosts. As usual, when the grant tables are modified directly, the server must be told to reload them (with `FLUSH PRIVILEGES') so that the privilege changes take effect. If you want to give a specific user access from any machine in a given domain, you can issue a `GRANT' statement like the following: mysql> GRANT ... ON *.* TO myusername@"%.mydomainname.com" IDENTIFIED BY 'mypassword'; To do the same thing by modifying the grant tables directly, do this: mysql> INSERT INTO user VALUES ('%.mydomainname.com', 'myusername', PASSWORD('mypassword'),...); mysql> FLUSH PRIVILEGES; You can also use `xmysqladmin', `mysql_webadmin', and even `xmysql' to insert, change, and update values in the grant tables. You can find these utilities in the Contrib directory of the *MySQL* Website (http://www.mysql.com/Downloads/Contrib/). Setting Up Passwords ==================== In most cases you should use `GRANT' to set up your users/passwords, so the following only applies for advanced users. *Note `GRANT': GRANT. The examples in the preceding sections illustrate an important principle: when you store a non-empty password using `INSERT' or `UPDATE' statements, you must use the `PASSWORD()' function to encrypt it. This is because the `user' table stores passwords in encrypted form, not as plaintext. If you forget that fact, you are likely to attempt to set passwords like this: shell> mysql -u root mysql mysql> INSERT INTO user (Host,User,Password) VALUES('%','jeffrey','biscuit'); mysql> FLUSH PRIVILEGES; The result is that the plaintext value `'biscuit'' is stored as the password in the `user' table. When the user `jeffrey' attempts to connect to the server using this password, the `mysql' client encrypts it with `PASSWORD()' and sends the result to the server. The server compares the value in the `user' table (the encrypted value of `'biscuit'') to the encrypted password (which is _not_ `'biscuit''). The comparison fails and the server rejects the connection: shell> mysql -u jeffrey -pbiscuit test Access denied Passwords must be encrypted when they are inserted in the `user' table, so the `INSERT' statement should have been specified like this instead: mysql> INSERT INTO user (Host,User,Password) VALUES('%','jeffrey',PASSWORD('biscuit')); You must also use the `PASSWORD()' function when you use `SET PASSWORD' statements: mysql> SET PASSWORD FOR jeffrey@"%" = PASSWORD('biscuit'); If you set passwords using the `GRANT ... IDENTIFIED BY' statement or the `mysqladmin password' command, the `PASSWORD()' function is unnecessary. They both take care of encrypting the password for you, so you would specify a password of `'biscuit'' like this: mysql> GRANT USAGE ON *.* TO jeffrey@"%" IDENTIFIED BY 'biscuit'; or shell> mysqladmin -u jeffrey password biscuit *NOTE:* `PASSWORD()' does not perform password encryption in the same way that Unix passwords are encrypted. You should not assume that if your Unix password and your *MySQL* password are the same, that `PASSWORD()' will result in the same encrypted value as is stored in the Unix password file. *Note User names::. Causes of `Access denied' Errors ================================ If you encounter `Access denied' errors when you try to connect to the *MySQL* server, the list below indicates some courses of action you can take to correct the problem: * After installing *MySQL*, did you run the `mysql_install_db' script to set up the initial grant table contents? If not, do so. *Note Default privileges::. Test the initial privileges by executing this command: shell> mysql -u root test The server should let you connect without error. You should also make sure you have a file `user.MYD' in the *MySQL* database directory. Ordinarily, this is `PATH/var/mysql/user.MYD', where `PATH' is the pathname to the *MySQL* installation root. * After a fresh installation, you should connect to the server and set up your users and their access permissions: shell> mysql -u root mysql The server should let you connect because the *MySQL* `root' user has no password initially. That is also a security risk, so setting the `root' password is something you should do while you're setting up your other *MySQL* users. If you try to connect as `root' and get this error: Access denied for user: '@unknown' to database mysql this means that you don't have an entry in the `user' table with a `User' column value of `'root'' and that `mysqld' cannot resolve the hostname for your client. In this case, you must restart the server with the `--skip-grant-tables' option and edit your `/etc/hosts' or `\windows\hosts' file to add an entry for your host. * If you get an error like the following: shell> mysqladmin -u root -pxxxx ver Access denied for user: 'root@localhost' (Using password: YES) It means that you are using a wrong password. *Note Passwords::. If you have forgot the root password, you can restart `mysqld' with `--skip-grant-tables' to change the password. You can find more about this option later on in this manual section. If you get the above error even if you haven't specified a password, this means that you a wrong password in some `my.ini' file. *Note Option files::. You can avoid using option files with the `--no-defaults' option, as follows: shell> mysqladmin --no-defaults -u root ver * If you updated an existing *MySQL* installation from a version earlier than Version 3.22.11 to Version 3.22.11 or later, did you run the `mysql_fix_privilege_tables' script? If not, do so. The structure of the grant tables changed with *MySQL* Version 3.22.11 when the `GRANT' statement became functional. * If your privileges seem to have changed in the middle of a session, it may be that a superuser has changed them. Reloading the grant tables affects new client connections, but it also affects existing connections as indicated in *Note Privilege changes::. * If you can't get your password to work, remember that you must use the `PASSWORD()' function if you set the password with the `INSERT', `UPDATE', or `SET PASSWORD' statements. The `PASSWORD()' function is unnecessary if you specify the password using the `GRANT ... INDENTIFIED BY' statement or the `mysqladmin password' command. *Note Passwords::. * `localhost' is a synonym for your local hostname, and is also the default host to which clients try to connect if you specify no host explicitly. However, connections to `localhost' do not work if you are running on a system that uses MIT-pthreads (`localhost' connections are made using Unix sockets, which are not supported by MIT-pthreads). To avoid this problem on such systems, you should use the `--host' option to name the server host explicitly. This will make a TCP/IP connection to the `mysqld' server. In this case, you must have your real hostname in `user' table entries on the server host. (This is true even if you are running a client program on the same host as the server.) * If you get an `Access denied' error when trying to connect to the database with `mysql -u user_name db_name', you may have a problem with the `user' table. Check this by executing `mysql -u root mysql' and issuing this SQL statement: mysql> SELECT * FROM user; The result should include an entry with the `Host' and `User' columns matching your computer's hostname and your *MySQL* user name. * The `Access denied' error message will tell you who you are trying to log in as, the host from which you are trying to connect, and whether or not you were using a password. Normally, you should have one entry in the `user' table that exactly matches the hostname and user name that were given in the error message. For example if you get an error message that contains `Using password: NO', this means that you tried to login without an password. * If you get the following error when you try to connect from a different host than the one on which the *MySQL* server is running, then there is no row in the `user' table that matches that host: Host ... is not allowed to connect to this MySQL server You can fix this by using the command-line tool `mysql' (on the server host!) to add a row to the `user', `db', or `host' table for the user/hostname combination from which you are trying to connect and then execute `mysqladmin flush-privileges'. If you are not running *MySQL* Version 3.22 and you don't know the IP number or hostname of the machine from which you are connecting, you should put an entry with `'%'' as the `Host' column value in the `user' table and restart `mysqld' with the `--log' option on the server machine. After trying to connect from the client machine, the information in the *MySQL* log will indicate how you really did connect. (Then replace the `'%'' in the `user' table entry with the actual hostname that shows up in the log. Otherwise, you'll have a system that is insecure.) Another reason for this error on Linux is that you are using a binary *MySQL* version that is compiled with a different glibc version than the one you are using. In this case you should either upgrade your OS/glibc or download the source *MySQL* version and compile this yourself. A source RPM is normally trivial to compile and install, so this isn't a big problem. * If you get an error message where the hostname is not shown or where the hostname is an IP, even if you try to connect with a hostname: shell> mysqladmin -u root -pxxxx -h some-hostname ver Access denied for user: 'root('Using password: YES) This means that *MySQL* got some error when trying to resolve the IP to a hostname. In this case you can execute `mysqladmin flush-hosts' to reset the internal DNS cache. *Note DNS::. Some permanent solutions are: - Try to find out what is wrong with your DNS server and fix this. - Specify IPs instead of hostnames in the *MySQL* privilege tables. - Start `mysqld' with `--skip-name-resolve'. - Start `mysqld' with `--skip-host-cache'. - Connect to `localhost' if you are running the server and the client on the same machine. - Put the client machine names in `/etc/hosts'. * If `mysql -u root test' works but `mysql -h your_hostname -u root test' results in `Access denied', then you may not have the correct name for your host in the `user' table. A common problem here is that the `Host' value in the user table entry specifies an unqualified hostname, but your system's name resolution routines return a fully qualified domain name (or vice-versa). For example, if you have an entry with host `'tcx'' in the `user' table, but your DNS tells *MySQL* that your hostname is `'tcx.subnet.se'', the entry will not work. Try adding an entry to the `user' table that contains the IP number of your host as the `Host' column value. (Alternatively, you could add an entry to the `user' table with a `Host' value that contains a wild card--for example, `'tcx.%''. However, use of hostnames ending with `%' is _insecure_ and is _not_ recommended!) * If `mysql -u user_name test' works but `mysql -u user_name other_db_name' doesn't work, you don't have an entry for `other_db_name' listed in the `db' table. * If `mysql -u user_name db_name' works when executed on the server machine, but `mysql -u host_name -u user_name db_name' doesn't work when executed on another client machine, you don't have the client machine listed in the `user' table or the `db' table. * If you can't figure out why you get `Access denied', remove from the `user' table all entries that have `Host' values containing wild cards (entries that contain `%' or `_'). A very common error is to insert a new entry with `Host'=`'%'' and `User'=`'some user'', thinking that this will allow you to specify `localhost' to connect from the same machine. The reason that this doesn't work is that the default privileges include an entry with `Host'=`'localhost'' and `User'=`'''. Because that entry has a `Host' value `'localhost'' that is more specific than `'%'', it is used in preference to the new entry when connecting from `localhost'! The correct procedure is to insert a second entry with `Host'=`'localhost'' and `User'=`'some_user'', or to remove the entry with `Host'=`'localhost'' and `User'=`'''. * If you get the following error, you may have a problem with the `db' or `host' table: Access to database denied If the entry selected from the `db' table has an empty value in the `Host' column, make sure there are one or more corresponding entries in the `host' table specifying which hosts the `db' table entry applies to. If you get the error when using the SQL commands `SELECT ... INTO OUTFILE' or `LOAD DATA INFILE', your entry in the `user' table probably doesn't have the *file* privilege enabled. * Remember that client programs will use connection parameters specified in configuration files or environment variables. *Note Environment variables::. If a client seems to be sending the wrong default connection parameters when you don't specify them on the command line, check your environment and the `.my.cnf' file in your home directory. You might also check the system-wide *MySQL* configuration files, though it is far less likely that client connection parameters will be specified there. *Note Option files::. If you get `Access denied' when you run a client without any options, make sure you haven't specified an old password in any of your option files! *Note Option files::. * If you make changes to the grant tables directly (using an `INSERT' or `UPDATE' statement) and your changes seem to be ignored, remember that you must issue a `FLUSH PRIVILEGES' statement or execute a `mysqladmin flush-privileges' command to cause the server to re-read the privilege tables. Otherwise your changes have no effect until the next time the server is restarted. Remember that after you set the `root' password with an `UPDATE' command, you won't need to specify it until after you flush the privileges, because the server won't know you've changed the password yet! * If you have access problems with a Perl, PHP, Python, or ODBC program, try to connect to the server with `mysql -u user_name db_name' or `mysql -u user_name -pyour_pass db_name'. If you are able to connect using the `mysql' client, there is a problem with your program and not with the access privileges. (Note that there is no space between `-p' and the password; you can also use the `--password=your_pass' syntax to specify the password. If you use the `-p' option alone, *MySQL* will prompt you for the password.) * For testing, start the `mysqld' daemon with the `--skip-grant-tables' option. Then you can change the *MySQL* grant tables and use the `mysqlaccess' script to check whether or not your modifications have the desired effect. When you are satisfied with your changes, execute `mysqladmin flush-privileges' to tell the `mysqld' server to start using the new grant tables. *Note:* Reloading the grant tables overrides the `--skip-grant-tables' option. This allows you to tell the server to begin using the grant tables again without bringing it down and restarting it. * If everything else fails, start the `mysqld' daemon with a debugging option (for example, `--debug=d,general,query'). This will print host and user information about attempted connections, as well as information about each command issued. *Note Making trace files::. * If you have any other problems with the *MySQL* grant tables and feel you must post the problem to the mailing list, always provide a dump of the *MySQL* grant tables. You can dump the tables with the `mysqldump mysql' command. As always, post your problem using the `mysqlbug' script. *Note Bug reports::. In some cases you may need to restart `mysqld' with `--skip-grant-tables' to run `mysqldump'. MySQL Language Reference ************************ *MySQL* has a very complex, but intuitive and easy to learn SQL interface. This chapter describes the various commands, types, and functions you will need to know in order to use *MySQL* efficiently and effectively. This chapter also serves as a reference to all functionality included in *MySQL*. In order to use this chapter effectively, you may find it useful to refer to the various indexes. Literals: How to Write Strings and Numbers ========================================== This section describes the various ways to write strings and numbers in *MySQL*. It also covers the various nuances and "gotchas" that you may run into when dealing with these basic types in *MySQL*. Strings ------- A string is a sequence of characters, surrounded by either single quote (`'') or double quote (`"') characters (only the single quote if you run in ANSI mode). Examples: 'a string' "another string" Within a string, certain sequences have special meaning. Each of these sequences begins with a backslash (`\'), known as the _escape character_. *MySQL* recognizes the following escape sequences: `\0' An ASCII 0 (`NUL') character. `\'' A single quote (`'') character. `\"' A double quote (`"') character. `\b' A backspace character. `\n' A newline character. `\r' A carriage return character. `\t' A tab character. `\z' ASCII(26) (Control-Z). This character can be encoded to allow you to go around the problem that ASCII(26) stands for END-OF-FILE on Windows. (ASCII(26) will cause problems if you try to use `mysql database < filename'). `\\' A backslash (`\') character. `\%' A `%' character. This is used to search for literal instances of `%' in contexts where `%' would otherwise be interpreted as a wild-card character. *Note String comparison functions::. `\_' A `_' character. This is used to search for literal instances of `_' in contexts where `_' would otherwise be interpreted as a wild-card character. *Note String comparison functions::. Note that if you use `\%' or `\_' in some string contexts, these will return the strings `\%' and `\_' and not `%' and `_'. There are several ways to include quotes within a string: * A `'' inside a string quoted with `'' may be written as `'''. * A `"' inside a string quoted with `"' may be written as `""'. * You can precede the quote character with an escape character (`\'). * A `'' inside a string quoted with `"' needs no special treatment and need not be doubled or escaped. In the same way, `"' inside a string quoted with `'' needs no special treatment. The `SELECT' statements shown below demonstrate how quoting and escaping work: mysql> SELECT 'hello', '"hello"', '""hello""', 'hel''lo', '\'hello'; +-------+---------+-----------+--------+--------+ | hello | "hello" | ""hello"" | hel'lo | 'hello | +-------+---------+-----------+--------+--------+ mysql> SELECT "hello", "'hello'", "''hello''", "hel""lo", "\"hello"; +-------+---------+-----------+--------+--------+ | hello | 'hello' | ''hello'' | hel"lo | "hello | +-------+---------+-----------+--------+--------+ mysql> SELECT "This\nIs\nFour\nlines"; +--------------------+ | This Is Four lines | +--------------------+ If you want to insert binary data into a `BLOB' column, the following characters must be represented by escape sequences: `NUL' ASCII 0. You should represent this by `\0' (a backslash and an ASCII `0' character). `\' ASCII 92, backslash. Represent this by `\\'. `'' ASCII 39, single quote. Represent this by `\''. `"' ASCII 34, double quote. Represent this by `\"'. If you write C code, you can use the C API function `mysql_escape_string()' to escape characters for the `INSERT' statement. *Note C API function overview::. In Perl, you can use the `quote' method of the `DBI' package to convert special characters to the proper escape sequences. *Note Perl `DBI' Class: Perl DBI Class. You should use an escape function on any string that might contain any of the special characters listed above! Numbers ------- Integers are represented as a sequence of digits. Floats use `.' as a decimal separator. Either type of number may be preceded by `-' to indicate a negative value. Examples of valid integers: 1221 0 -32 Examples of valid floating-point numbers: 294.42 -32032.6809e+10 148.00 An integer may be used in a floating-point context; it is interpreted as the equivalent floating-point number. Hexadecimal Values ------------------ *MySQL* supports hexadecimal values. In number context these act like an integer (64-bit precision). In string context these act like a binary string where each pair of hex digits is converted to a character: mysql> SELECT 0xa+0; -> 10 mysql> select 0x5061756c; -> Paul Hexadecimal strings are often used by ODBC to give values for BLOB columns. `NULL' Values ------------- The `NULL' value means "no data" and is different from values such as `0' for numeric types or the empty string for string types. *Note Problems with `NULL': Problems with NULL. `NULL' may be represented by `\N' when using the text file import or export formats (`LOAD DATA INFILE', `SELECT ... INTO OUTFILE'). *Note `LOAD DATA': LOAD DATA. Database, Table, Index, Column, and Alias Names ----------------------------------------------- Database, table, index, column, and alias names all follow the same rules in *MySQL*. Note that the rules changed starting with *MySQL* Version 3.23.6 when we introduced quoting of identifiers (database, table, and column names) with ``'. `"' will also work to quote identifiers if you run in ANSI mode. *Note ANSI mode::. *Identifier**Max *Allowed characters* length* Database 64 Any character that is allowed in a directory name except `/' or `.'. Table 64 Any character that is allowed in a file name, except `/' or `.'. Column 64 All characters. Alias 255 All characters. Note that in addition to the above, you can't have ASCII(0) or ASCII(255) or the quoting character in an identifier. Note that if the identifier is a restricted word or contains special characters you must always quote it with ``' when you use it: SELECT * from `select` where `select`.id > 100; In previous versions of *MySQL*, the name rules are as follows: * A name may consist of alphanumeric characters from the current character set and also `_' and `$'. The default character set is ISO-8859-1 Latin1; this may be changed with the `--default-character-set' option to `mysqld'. *Note Character sets::. * A name may start with any character that is legal in a name. In particular, a name may start with a number (this differs from many other database systems!). However, a name cannot consist _only_ of numbers. * You cannot use the `.' character in names because it is used to extend the format by which you can refer to columns (see immediately below). It is recommended that you do not use names like `1e', because an expression like `1e+1' is ambiguous. It may be interpreted as the expression `1e + 1' or as the number `1e+1'. In *MySQL* you can refer to a column using any of the following forms: *Column reference* *Meaning* `col_name' Column `col_name' from whichever table used in the query contains a column of that name. `tbl_name.col_name' Column `col_name' from table `tbl_name' of the current database. `db_name.tbl_name.col_name'Column `col_name' from table `tbl_name' of the database `db_name'. This form is available in *MySQL* Version 3.22 or later. ``column_name`' A column that is a keyword or contains special characters. You need not specify a `tbl_name' or `db_name.tbl_name' prefix for a column reference in a statement unless the reference would be ambiguous. For example, suppose tables `t1' and `t2' each contain a column `c', and you retrieve `c' in a `SELECT' statement that uses both `t1' and `t2'. In this case, `c' is ambiguous because it is not unique among the tables used in the statement, so you must indicate which table you mean by writing `t1.c' or `t2.c'. Similarly, if you are retrieving from a table `t' in database `db1' and from a table `t' in database `db2', you must refer to columns in those tables as `db1.t.col_name' and `db2.t.col_name'. The syntax `.tbl_name' means the table `tbl_name' in the current database. This syntax is accepted for ODBC compatibility, because some ODBC programs prefix table names with a `.' character. Case Sensitivity in Names ......................... In *MySQL*, databases and tables correspond to directories and files within those directories. Consequently, the case sensitivity of the underlying operating system determines the case sensitivity of database and table names. This means database and table names are case sensitive in Unix and case insensitive in Windows. *Note Extensions to ANSI::. *NOTE:* Although database and table names are case insensitive for Windows, you should not refer to a given database or table using different cases within the same query. The following query would not work because it refers to a table both as `my_table' and as `MY_TABLE': mysql> SELECT * FROM my_table WHERE MY_TABLE.col=1; Column names are case insensitive in all cases. Aliases on tables are case sensitive. The following query would not work because it refers to the alias both as `a' and as `A': mysql> SELECT col_name FROM tbl_name AS a WHERE a.col_name = 1 OR A.col_name = 2; Aliases on columns are case insensitive. If you have a problem remembering the used cases for a table names, adopt a consistent convention, such as always creating databases and tables using lowercase names. One way to avoid this problem is to start `mysqld' with `-O lower_case_table_names=1'. By default this option is 1 on Windows and 0 on Unix. If `lower_case_table_names' is 1 *MySQL* will convert all table names to lower case on storage and lookup. Note that if you change this option, you need to first convert your old table names to lower case before starting `mysqld'. User Variables ============== *MySQL* supports thread-specific variables with the `@variablename' syntax. A variable name may consist of alphanumeric characters from the current character set and also `_', `$', and `.' . The default character set is ISO-8859-1 Latin1; this may be changed with the `--default-character-set' option to `mysqld'. *Note Character sets::. Variables don't have to be initialized. They contain `NULL' by default and can store an integer, real, or string value. All variables for a thread are automatically freed when the thread exits. You can set a variable with the `SET' syntax: SET @variable= { integer expression | real expression | string expression } [,@variable= ...]. You can also set a variable in an expression with the `@variable:=expr' syntax: select @t1:=(@t2:=1)+@t3:=4,@t1,@t2,@t3; +----------------------+------+------+------+ | @t1:=(@t2:=1)+@t3:=4 | @t1 | @t2 | @t3 | +----------------------+------+------+------+ | 5 | 5 | 1 | 4 | +----------------------+------+------+------+ (We had to use the `:=' syntax here, because `=' was reserved for comparisons.) User variables may be used where expressions are allowed. Note that this does not currently include use in contexts where a number is explicitly required, such as in the `LIMIT' clause of a `SELECT' statement, or the `IGNORE number LINES' clause of a `LOAD DATA' statement. *NOTE:* In a `SELECT' statement, each expression is only evaluated when it's sent to the client. This means that in the `HAVING', `GROUP BY', or `ORDER BY' clause, you can't refer to an expression that involves variables that are set in the `SELECT' part. For example, the following statement will NOT work as expected: SELECT (@aa:=id) AS a, (@aa+3) AS b FROM table_name HAVING b=5; The reason is that `@aa' will not contain the value of the current row, but the value of `id' for the previous accepted row. Column Types ============ *MySQL* supports a number of column types, which may be grouped into three categories: numeric types, date and time types, and string (character) types. This section first gives an overview of the types available and summarizes the storage requirements for each column type, then provides a more detailed description of the properties of the types in each category. The overview is intentionally brief. The more detailed descriptions should be consulted for additional information about particular column types, such as the allowable formats in which you can specify values. The column types supported by *MySQL* are listed below. The following code letters are used in the descriptions: `M' Indicates the maximum display size. The maximum legal display size is 255. `D' Applies to floating-point types and indicates the number of digits following the decimal point. The maximum possible value is 30, but should be no greater than `M'-2. Square brackets (`[' and `]') indicate parts of type specifiers that are optional. Note that if you specify `ZEROFILL' for a column, *MySQL* will automatically add the `UNSIGNED' attribute to the column. `TINYINT[(M)] [UNSIGNED] [ZEROFILL]' A very small integer. The signed range is `-128' to `127'. The unsigned range is `0' to `255'. `SMALLINT[(M)] [UNSIGNED] [ZEROFILL]' A small integer. The signed range is `-32768' to `32767'. The unsigned range is `0' to `65535'. `MEDIUMINT[(M)] [UNSIGNED] [ZEROFILL]' A medium-size integer. The signed range is `-8388608' to `8388607'. The unsigned range is `0' to `16777215'. `INT[(M)] [UNSIGNED] [ZEROFILL]' A normal-size integer. The signed range is `-2147483648' to `2147483647'. The unsigned range is `0' to `4294967295'. `INTEGER[(M)] [UNSIGNED] [ZEROFILL]' This is a synonym for `INT'. `BIGINT[(M)] [UNSIGNED] [ZEROFILL]' A large integer. The signed range is `-9223372036854775808' to `9223372036854775807'. The unsigned range is `0' to `18446744073709551615'. Some things you should be aware about `BIGINT' columns: * As all arithmetic is done using signed `BIGINT' or `DOUBLE' values, so you shouldn't use unsigned big integers larger than `9223372036854775807' (63 bits) except with bit functions! If you do that, some of the last digits in the result may be wrong because of rounding errors when converting the `BIGINT' to a `DOUBLE'. * You can always store an exact integer value in a `BIGINT' column by storing it as a string, as there is in this case there will be no intermediate double representation. * `-', `+', and `*' will use `BIGINT' arithmetic when both arguments are `INTEGER' values! This means that if you multiply two big integers (or results from functions that return integers) you may get unexpected results when the result is larger than `9223372036854775807'. `FLOAT(precision) [ZEROFILL]' A floating-point number. Cannot be unsigned. `precision' can be `<=24' for a single-precision floating-point number and between 25 and 53 for a double-precision floating-point number. These types are like the `FLOAT' and `DOUBLE' types described immediately below. `FLOAT(X)' has the same range as the corresponding `FLOAT' and `DOUBLE' types, but the display size and number of decimals is undefined. In *MySQL* Version 3.23, this is a true floating-point value. In earlier *MySQL* versions, `FLOAT(precision)' always has 2 decimals. Note that using `FLOAT' may give you some unexpected problems as all calculation in *MySQL* is done with double precision. *Note No matching rows::. This syntax is provided for ODBC compatibility. `FLOAT[(M,D)] [ZEROFILL]' A small (single-precision) floating-point number. Cannot be unsigned. Allowable values are `-3.402823466E+38' to `-1.175494351E-38', `0', and `1.175494351E-38' to `3.402823466E+38'. The M is the display width and D is the number of decimals. `FLOAT' without an argument or with an argument of <= 24 stands for a single-precision floating-point number. `DOUBLE[(M,D)] [ZEROFILL]' A normal-size (double-precision) floating-point number. Cannot be unsigned. Allowable values are `-1.7976931348623157E+308' to `-2.2250738585072014E-308', `0', and `2.2250738585072014E-308' to `1.7976931348623157E+308'. The M is the display width and D is the number of decimals. `DOUBLE' without an argument or `FLOAT(X)' where 25 <= X <= 53 stands for a double-precision floating-point number. `DOUBLE PRECISION[(M,D)] [ZEROFILL]' `REAL[(M,D)] [ZEROFILL]' These are synonyms for `DOUBLE'. `DECIMAL[(M[,D])] [ZEROFILL]' An unpacked floating-point number. Cannot be unsigned. Behaves like a `CHAR' column: "unpacked" means the number is stored as a string, using one character for each digit of the value. The decimal point and, for negative numbers, the `-' sign, are not counted in M (but space for these are reserved). If `D' is 0, values will have no decimal point or fractional part. The maximum range of `DECIMAL' values is the same as for `DOUBLE', but the actual range for a given `DECIMAL' column may be constrained by the choice of `M' and `D'. If `D' is left out it's set to 0. If `M' is left out it's set to 10. Note that in *MySQL* Version 3.22 the `M' argument had to includes the space needed for the sign and the decimal point. `NUMERIC(M,D) [ZEROFILL]' This is a synonym for `DECIMAL'. `DATE' A date. The supported range is `'1000-01-01'' to `'9999-12-31''. *MySQL* displays `DATE' values in `'YYYY-MM-DD'' format, but allows you to assign values to `DATE' columns using either strings or numbers. *Note DATETIME::. `DATETIME' A date and time combination. The supported range is `'1000-01-01 00:00:00'' to `'9999-12-31 23:59:59''. *MySQL* displays `DATETIME' values in `'YYYY-MM-DD HH:MM:SS'' format, but allows you to assign values to `DATETIME' columns using either strings or numbers. *Note DATETIME::. `TIMESTAMP[(M)]' A timestamp. The range is `'1970-01-01 00:00:00'' to sometime in the year `2037'. *MySQL* displays `TIMESTAMP' values in `YYYYMMDDHHMMSS', `YYMMDDHHMMSS', `YYYYMMDD', or `YYMMDD' format, depending on whether `M' is `14' (or missing), `12', `8', or `6', but allows you to assign values to `TIMESTAMP' columns using either strings or numbers. A `TIMESTAMP' column is useful for recording the date and time of an `INSERT' or `UPDATE' operation because it is automatically set to the date and time of the most recent operation if you don't give it a value yourself. You can also set it to the current date and time by assigning it a `NULL' value. *Note Date and time types::. A `TIMESTAMP' is always stored in 4 bytes. The `M' argument only affects how the `TIMESTAMP' column is displayed. Note that `TIMESTAMP(X)' columns where X is 8 or 14 are reported to be numbers while other `TIMESTAMP(X)' columns are reported to be strings. This is just to ensure that one can reliably dump and restore the table with these types! *Note DATETIME::. `TIME' A time. The range is `'-838:59:59'' to `'838:59:59''. *MySQL* displays `TIME' values in `'HH:MM:SS'' format, but allows you to assign values to `TIME' columns using either strings or numbers. *Note TIME::. `YEAR[(2|4)]' A year in 2- or 4-digit format (default is 4-digit). The allowable values are `1901' to `2155', `0000' in the 4-digit year format, and 1970-2069 if you use the 2-digit format (70-69). *MySQL* displays `YEAR' values in `YYYY' format, but allows you to assign values to `YEAR' columns using either strings or numbers. (The `YEAR' type is new in *MySQL* Version 3.22.). *Note YEAR::. `[NATIONAL] CHAR(M) [BINARY]' A fixed-length string that is always right-padded with spaces to the specified length when stored. The range of `M' is 1 to 255 characters. Trailing spaces are removed when the value is retrieved. `CHAR' values are sorted and compared in case-insensitive fashion according to the default character set unless the `BINARY' keyword is given. `NATIONAL CHAR' (short form `NCHAR') is the ANSI SQL way to define that a CHAR column should use the default CHARACTER set. This is the default in *MySQL*. `CHAR' is a shorthand for `CHARACTER'. *MySQL* allows you to create a column of type `CHAR(0)'. This is mainly useful when you have to be compliant with some old applications that depend on the existence of a column but that do not actually use the value. This is also quite nice when you need a column that only can take 2 values: A `CHAR(0)', that is not defined as `NOT NULL', will only occupy one bit and can only take 2 values: `NULL' or `""'. *Note CHAR::. `[NATIONAL] VARCHAR(M) [BINARY]' A variable-length string. *NOTE:* Trailing spaces are removed when the value is stored (this differs from the ANSI SQL specification). The range of `M' is 1 to 255 characters. `VARCHAR' values are sorted and compared in case-insensitive fashion unless the `BINARY' keyword is given. *Note Silent column changes::. `VARCHAR' is a shorthand for `CHARACTER VARYING'. *Note CHAR::. `TINYBLOB' `TINYTEXT' A `BLOB' or `TEXT' column with a maximum length of 255 (2^8 - 1) characters. *Note Silent column changes::. *Note BLOB::. `BLOB' `TEXT' A `BLOB' or `TEXT' column with a maximum length of 65535 (2^16 - 1) characters. *Note Silent column changes::. *Note BLOB::. `MEDIUMBLOB' `MEDIUMTEXT' A `BLOB' or `TEXT' column with a maximum length of 16777215 (2^24 - 1) characters. *Note Silent column changes::. *Note BLOB::. `LONGBLOB' `LONGTEXT' A `BLOB' or `TEXT' column with a maximum length of 4294967295 (2^32 - 1) characters. *Note Silent column changes::. Note that because the server/client protocol and MyISAM tables has currently a limit of 16M per communication packet / table row, you can't yet use this the whole range of this type. *Note BLOB::. `ENUM('value1','value2',...)' An enumeration. A string object that can have only one value, chosen from the list of values `'value1'', `'value2'', `...', `NULL' or the special `""' error value. An `ENUM' can have a maximum of 65535 distinct values. *Note ENUM::. `SET('value1','value2',...)' A set. A string object that can have zero or more values, each of which must be chosen from the list of values `'value1'', `'value2'', `...' A `SET' can have a maximum of 64 members. *Note SET::. Column Type Storage Requirements -------------------------------- The storage requirements for each of the column types supported by *MySQL* are listed below by category. Storage requirements for numeric types ...................................... *Column type* *Storage required* `TINYINT' 1 byte `SMALLINT' 2 bytes `MEDIUMINT' 3 bytes `INT' 4 bytes `INTEGER' 4 bytes `BIGINT' 8 bytes `FLOAT(X)' 4 if X <= 24 or 8 if 25 <= X <= 53 `FLOAT' 4 bytes `DOUBLE' 8 bytes `DOUBLE PRECISION' 8 bytes `REAL' 8 bytes `DECIMAL(M,D)' `M+2' bytes if D > 0, `M+1' bytes if D = 0 (`D'+2, if `M < D') `NUMERIC(M,D)' `M+2' bytes if D > 0, `M+1' bytes if D = 0 (`D'+2, if `M < D') Storage requirements for date and time types ............................................ *Column type* *Storage required* `DATE' 3 bytes `DATETIME' 8 bytes `TIMESTAMP' 4 bytes `TIME' 3 bytes `YEAR' 1 byte Storage requirements for string types ..................................... *Column type* *Storage required* `CHAR(M)' `M' bytes, `1 <= M <= 255' `VARCHAR(M)' `L'+1 bytes, where `L <= M' and `1 <= M <= 255' `TINYBLOB', `TINYTEXT' `L'+1 bytes, where `L' < 2^8 `BLOB', `TEXT' `L'+2 bytes, where `L' < 2^16 `MEDIUMBLOB', `MEDIUMTEXT' `L'+3 bytes, where `L' < 2^24 `LONGBLOB', `LONGTEXT' `L'+4 bytes, where `L' < 2^32 `ENUM('value1','value2',...)' 1 or 2 bytes, depending on the number of enumeration values (65535 values maximum) `SET('value1','value2',...)' 1, 2, 3, 4 or 8 bytes, depending on the number of set members (64 members maximum) `VARCHAR' and the `BLOB' and `TEXT' types are variable-length types, for which the storage requirements depend on the actual length of column values (represented by `L' in the preceding table), rather than on the type's maximum possible size. For example, a `VARCHAR(10)' column can hold a string with a maximum length of 10 characters. The actual storage required is the length of the string (`L'), plus 1 byte to record the length of the string. For the string `'abcd'', `L' is 4 and the storage requirement is 5 bytes. The `BLOB' and `TEXT' types require 1, 2, 3, or 4 bytes to record the length of the column value, depending on the maximum possible length of the type. *Note BLOB::. If a table includes any variable-length column types, the record format will also be variable-length. Note that when a table is created, *MySQL* may, under certain conditions, change a column from a variable-length type to a fixed-length type, or vice-versa. *Note Silent column changes::. The size of an `ENUM' object is determined by the number of different enumeration values. One byte is used for enumerations with up to 255 possible values. Two bytes are used for enumerations with up to 65535 values. *Note ENUM::. The size of a `SET' object is determined by the number of different set members. If the set size is `N', the object occupies `(N+7)/8' bytes, rounded up to 1, 2, 3, 4, or 8 bytes. A `SET' can have a maximum of 64 members. *Note SET::. Numeric Types ------------- *MySQL* supports all of the ANSI/ISO SQL92 numeric types. These types include the exact numeric data types (`NUMERIC', `DECIMAL', `INTEGER', and `SMALLINT'), as well as the approximate numeric data types (`FLOAT', `REAL', and `DOUBLE PRECISION'). The keyword `INT' is a synonym for `INTEGER', and the keyword `DEC' is a synonym for `DECIMAL'. The `NUMERIC' and `DECIMAL' types are implemented as the same type by *MySQL*, as permitted by the SQL92 standard. They are used for values for which it is important to preserve exact precision, for example with monetary data. When declaring a column of one of these types the precision and scale can be (and usually is) specified; for example: salary DECIMAL(9,2) In this example, `9' (`precision') represents the number of significant decimal digits that will be stored for values, and `2' (`scale') represents the number of digits that will be stored following the decimal point. In this case, therefore, the range of values that can be stored in the `salary' column is from `-9999999.99' to `9999999.99'. In ANSI/ISO SQL92, the syntax `DECIMAL(p)' is equivalent to `DECIMAL(p,0)'. Similarly, the syntax `DECIMAL' is equivalent to `DECIMAL(p,0)', where the implementation is allowed to decide the value of `p'. *MySQL* does not currently support either of these variant forms of the `DECIMAL'/`NUMERIC' data types. This is not generally a serious problem, as the principal benefits of these types derive from the ability to control both precision and scale explicitly. `DECIMAL' and `NUMERIC' values are stored as strings, rather than as binary floating-point numbers, in order to preserve the decimal precision of those values. One character is used for each digit of the value, the decimal point (if `scale' > 0), and the `-' sign (for negative numbers). If `scale' is 0, `DECIMAL' and `NUMERIC' values contain no decimal point or fractional part. The maximum range of `DECIMAL' and `NUMERIC' values is the same as for `DOUBLE', but the actual range for a given `DECIMAL' or `NUMERIC' column can be constrained by the `precision' or `scale' for a given column. When such a column is assigned a value with more digits following the decimal point than are allowed by the specified `scale', the value is rounded to that `scale'. When a `DECIMAL' or `NUMERIC' column is assigned a value whose magnitude exceeds the range implied by the specified (or defaulted) `precision' and `scale', *MySQL* stores the value representing the corresponding end point of that range. As an extension to the ANSI/ISO SQL92 standard, *MySQL* also supports the integral types `TINYINT', `MEDIUMINT', and `BIGINT' as listed in the tables above. Another extension is supported by *MySQL* for optionally specifying the display width of an integral value in parentheses following the base keyword for the type (for example, `INT(4)'). This optional width specification is used to left-pad the display of values whose width is less than the width specified for the column, but does not constrain the range of values that can be stored in the column, nor the number of digits that will be displayed for values whose width exceeds that specified for the column. When used in conjunction with the optional extension attribute `ZEROFILL', the default padding of spaces is replaced with zeroes. For example, for a column declared as `INT(5) ZEROFILL', a value of `4' is retrieved as `00004'. Note that if you store larger values than the display width in an integer column, you may experience problems when *MySQL* generates temporary tables for some complicated joins, as in these cases *MySQL* trusts that the data did fit into the original column width. All integral types can have an optional (non-standard) attribute `UNSIGNED'. Unsigned values can be used when you want to allow only positive numbers in a column and you need a little bigger numeric range for the column. The `FLOAT' type is used to represent approximate numeric data types. The ANSI/ISO SQL92 standard allows an optional specification of the precision (but not the range of the exponent) in bits following the keyword `FLOAT' in parentheses. The *MySQL* implementation also supports this optional precision specification. When the keyword `FLOAT' is used for a column type without a precision specification, *MySQL* uses four bytes to store the values. A variant syntax is also supported, with two numbers given in parentheses following the `FLOAT' keyword. With this option, the first number continues to represent the storage requirements for the value in bytes, and the second number specifies the number of digits to be stored and displayed following the decimal point (as with `DECIMAL' and `NUMERIC'). When *MySQL* is asked to store a number for such a column with more decimal digits following the decimal point than specified for the column, the value is rounded to eliminate the extra digits when the value is stored. The `REAL' and `DOUBLE PRECISION' types do not accept precision specifications. As an extension to the ANSI/ISO SQL92 standard, *MySQL* recognizes `DOUBLE' as a synonym for the `DOUBLE PRECISION' type. In contrast with the standard's requirement that the precision for `REAL' be smaller than that used for `DOUBLE PRECISION', *MySQL* implements both as 8-byte double-precision floating-point values (when not running in "ANSI mode"). For maximum portability, code requiring storage of approximate numeric data values should use `FLOAT' or `DOUBLE PRECISION' with no specification of precision or number of decimal points. When asked to store a value in a numeric column that is outside the column type's allowable range, *MySQL* clips the value to the appropriate endpoint of the range and stores the resulting value instead. For example, the range of an `INT' column is `-2147483648' to `2147483647'. If you try to insert `-9999999999' into an `INT' column, the value is clipped to the lower endpoint of the range, and `-2147483648' is stored instead. Similarly, if you try to insert `9999999999', `2147483647' is stored instead. If the `INT' column is `UNSIGNED', the size of the column's range is the same but its endpoints shift up to `0' and `4294967295'. If you try to store `-9999999999' and `9999999999', the values stored in the column become `0' and `4294967296'. Conversions that occur due to clipping are reported as "warnings" for `ALTER TABLE', `LOAD DATA INFILE', `UPDATE', and multi-row `INSERT' statements. Date and Time Types ------------------- The date and time types are `DATETIME', `DATE', `TIMESTAMP', `TIME', and `YEAR'. Each of these has a range of legal values, as well as a "zero" value that is used when you specify a really illegal value. Note that *MySQL* allows you to store certain 'not strictly' legal date values, for example `1999-11-31'. The reason for this is that we think it's the responsibility of the application to handle date checking, not the SQL servers. To make the date checking 'fast', *MySQL* only checks that the month is in the range of 0-12 and the day is in the range of 0-31. The above ranges are defined this way because *MySQL* allows you to store, in a `DATE' or `DATETIME' column, dates where the day or month-day is zero. This is extremely useful for applications that need to store a birth-date for which you don't know the exact date. In this case you simply store the date like `1999-00-00' or `1999-01-00'. (You cannot expect to get a correct value from functions like `DATE_SUB()' or `DATE_ADD' for dates like these.) Here are some general considerations to keep in mind when working with date and time types: * *MySQL* retrieves values for a given date or time type in a standard format, but it attempts to interpret a variety of formats for values that you supply (for example, when you specify a value to be assigned to or compared to a date or time type). Nevertheless, only the formats described in the following sections are supported. It is expected that you will supply legal values, and unpredictable results may occur if you use values in other formats. * Although *MySQL* tries to interpret values in several formats, it always expects the year part of date values to be leftmost. Dates must be given in year-month-day order (for example, `'98-09-04''), rather than in the month-day-year or day-month-year orders commonly used elsewhere (for example, `'09-04-98'', `'04-09-98''). * *MySQL* automatically converts a date or time type value to a number if the value is used in a numeric context, and vice versa. * When *MySQL* encounters a value for a date or time type that is out of range or otherwise illegal for the type (see the start of this section), it converts the value to the "zero" value for that type. (The exception is that out-of-range `TIME' values are clipped to the appropriate endpoint of the `TIME' range.) The table below shows the format of the "zero" value for each type: *Column type* *"Zero" value* `DATETIME' `'0000-00-00 00:00:00'' `DATE' `'0000-00-00'' `TIMESTAMP' `00000000000000' (length depends on display size) `TIME' `'00:00:00'' `YEAR' `0000' * The "zero" values are special, but you can store or refer to them explicitly using the values shown in the table. You can also do this using the values `'0'' or `0', which are easier to write. * "Zero" date or time values used through *MyODBC* are converted automatically to `NULL' in *MyODBC* Version 2.50.12 and above, because ODBC can't handle such values. Y2K Issues and Date Types ......................... *MySQL* itself is Y2K-safe (*note Year 2000 compliance::), but input values presented to *MySQL* may not be. Any input containing 2-digit year values is ambiguous, because the century is unknown. Such values must be interpreted into 4-digit form because *MySQL* stores years internally using four digits. For `DATETIME', `DATE', `TIMESTAMP', and `YEAR' types, *MySQL* interprets dates with ambiguous year values using the following rules: * Year values in the range `00-69' are converted to `2000-2069'. * Year values in the range `70-99' are converted to `1970-1999'. Remember that these rules provide only reasonable guesses as to what your data mean. If the heuristics used by *MySQL* don't produce the correct values, you should provide unambiguous input containing 4-digit year values. `ORDER BY' will sort 2-digit `YEAR/DATE/DATETIME' types properly. Note also that some functions like `MIN()' and `MAX()' will convert a `TIMESTAMP/DATE' to a number. This means that a timestamp with a 2-digit year will not work properly with these functions. The fix in this case is to convert the `TIMESTAMP/DATE' to 4-digit year format or use something like `MIN(DATE_ADD(timestamp,INTERVAL 0 DAYS))'. The `DATETIME', `DATE', and `TIMESTAMP' Types ............................................. The `DATETIME', `DATE', and `TIMESTAMP' types are related. This section describes their characteristics, how they are similar, and how they differ. The `DATETIME' type is used when you need values that contain both date and time information. *MySQL* retrieves and displays `DATETIME' values in `'YYYY-MM-DD HH:MM:SS'' format. The supported range is `'1000-01-01 00:00:00'' to `'9999-12-31 23:59:59''. ("Supported" means that although earlier values might work, there is no guarantee that they will.) The `DATE' type is used when you need only a date value, without a time part. *MySQL* retrieves and displays `DATE' values in `'YYYY-MM-DD'' format. The supported range is `'1000-01-01'' to `'9999-12-31''. The `TIMESTAMP' column type provides a type that you can use to automatically mark `INSERT' or `UPDATE' operations with the current date and time. If you have multiple `TIMESTAMP' columns, only the first one is updated automatically. Automatic updating of the first `TIMESTAMP' column occurs under any of the following conditions: * The column is not specified explicitly in an `INSERT' or `LOAD DATA INFILE' statement. * The column is not specified explicitly in an `UPDATE' statement and some other column changes value. (Note that an `UPDATE' that sets a column to the value it already has will not cause the `TIMESTAMP' column to be updated, because if you set a column to its current value, *MySQL* ignores the update for efficiency.) * You explicitly set the `TIMESTAMP' column to `NULL'. `TIMESTAMP' columns other than the first may also be set to the current date and time. Just set the column to `NULL' or to `NOW()'. You can set any `TIMESTAMP' column to a value different than the current date and time by setting it explicitly to the desired value. This is true even for the first `TIMESTAMP' column. You can use this property if, for example, you want a `TIMESTAMP' to be set to the current date and time when you create a row, but not to be changed whenever the row is updated later: * Let *MySQL* set the column when the row is created. This will initialize it to the current date and time. * When you perform subsequent updates to other columns in the row, set the `TIMESTAMP' column explicitly to its current value. On the other hand, you may find it just as easy to use a `DATETIME' column that you initialize to `NOW()' when the row is created and leave alone for subsequent updates. `TIMESTAMP' values may range from the beginning of 1970 to sometime in the year 2037, with a resolution of one second. Values are displayed as numbers. The format in which *MySQL* retrieves and displays `TIMESTAMP' values depends on the display size, as illustrated by the table below. The `full' `TIMESTAMP' format is 14 digits, but `TIMESTAMP' columns may be created with shorter display sizes: *Column type* *Display format* `TIMESTAMP(14)' `YYYYMMDDHHMMSS' `TIMESTAMP(12)' `YYMMDDHHMMSS' `TIMESTAMP(10)' `YYMMDDHHMM' `TIMESTAMP(8)' `YYYYMMDD' `TIMESTAMP(6)' `YYMMDD' `TIMESTAMP(4)' `YYMM' `TIMESTAMP(2)' `YY' All `TIMESTAMP' columns have the same storage size, regardless of display size. The most common display sizes are 6, 8, 12, and 14. You can specify an arbitrary display size at table creation time, but values of 0 or greater than 14 are coerced to 14. Odd-valued sizes in the range from 1 to 13 are coerced to the next higher even number. You can specify `DATETIME', `DATE', and `TIMESTAMP' values using any of a common set of formats: * As a string in either `'YYYY-MM-DD HH:MM:SS'' or `'YY-MM-DD HH:MM:SS'' format. A "relaxed" syntax is allowed--any punctuation character may be used as the delimiter between date parts or time parts. For example, `'98-12-31 11:30:45'', `'98.12.31 11+30+45'', `'98/12/31 11*30*45'', and `'98@12@31 11^30^45'' are equivalent. * As a string in either `'YYYY-MM-DD'' or `'YY-MM-DD'' format. A "relaxed" syntax is allowed here, too. For example, `'98-12-31'', `'98.12.31'', `'98/12/31'', and `'98@12@31'' are equivalent. * As a string with no delimiters in either `'YYYYMMDDHHMMSS'' or `'YYMMDDHHMMSS'' format, provided that the string makes sense as a date. For example, `'19970523091528'' and `'970523091528'' are interpreted as `'1997-05-23 09:15:28'', but `'971122129015'' is illegal (it has a nonsensical minute part) and becomes `'0000-00-00 00:00:00''. * As a string with no delimiters in either `'YYYYMMDD'' or `'YYMMDD'' format, provided that the string makes sense as a date. For example, `'19970523'' and `'970523'' are interpreted as `'1997-05-23'', but `'971332'' is illegal (it has nonsensical month and day parts) and becomes `'0000-00-00''. * As a number in either `YYYYMMDDHHMMSS' or `YYMMDDHHMMSS' format, provided that the number makes sense as a date. For example, `19830905132800' and `830905132800' are interpreted as `'1983-09-05 13:28:00''. * As a number in either `YYYYMMDD' or `YYMMDD' format, provided that the number makes sense as a date. For example, `19830905' and `830905' are interpreted as `'1983-09-05''. * As the result of a function that returns a value that is acceptable in a `DATETIME', `DATE', or `TIMESTAMP' context, such as `NOW()' or `CURRENT_DATE'. Illegal `DATETIME', `DATE', or `TIMESTAMP' values are converted to the "zero" value of the appropriate type (`'0000-00-00 00:00:00'', `'0000-00-00'', or `00000000000000'). For values specified as strings that include date part delimiters, it is not necessary to specify two digits for month or day values that are less than `10'. `'1979-6-9'' is the same as `'1979-06-09''. Similarly, for values specified as strings that include time part delimiters, it is not necessary to specify two digits for hour, month, or second values that are less than `10'. `'1979-10-30 1:2:3'' is the same as `'1979-10-30 01:02:03''. Values specified as numbers should be 6, 8, 12, or 14 digits long. If the number is 8 or 14 digits long, it is assumed to be in `YYYYMMDD' or `YYYYMMDDHHMMSS' format and that the year is given by the first 4 digits. If the number is 6 or 12 digits long, it is assumed to be in `YYMMDD' or `YYMMDDHHMMSS' format and that the year is given by the first 2 digits. Numbers that are not one of these lengths are interpreted as though padded with leading zeros to the closest length. Values specified as non-delimited strings are interpreted using their length as given. If the string is 8 or 14 characters long, the year is assumed to be given by the first 4 characters. Otherwise the year is assumed to be given by the first 2 characters. The string is interpreted from left to right to find year, month, day, hour, minute, and second values, for as many parts as are present in the string. This means you should not use strings that have fewer than 6 characters. For example, if you specify `'9903'', thinking that will represent March, 1999, you will find that *MySQL* inserts a "zero" date into your table. This is because the year and month values are `99' and `03', but the day part is missing (zero), so the value is not a legal date. `TIMESTAMP' columns store legal values using the full precision with which the value was specified, regardless of the display size. This has several implications: * Always specify year, month, and day, even if your column types are `TIMESTAMP(4)' or `TIMESTAMP(2)'. Otherwise, the value will not be a legal date and `0' will be stored. * If you use `ALTER TABLE' to widen a narrow `TIMESTAMP' column, information will be displayed that previously was "hidden". * Similarly, narrowing a `TIMESTAMP' column does not cause information to be lost, except in the sense that less information is shown when the values are displayed. * Although `TIMESTAMP' values are stored to full precision, the only function that operates directly on the underlying stored value is `UNIX_TIMESTAMP()'. Other functions operate on the formatted retrieved value. This means you cannot use functions such as `HOUR()' or `SECOND()' unless the relevant part of the `TIMESTAMP' value is included in the formatted value. For example, the `HH' part of a `TIMESTAMP' column is not displayed unless the display size is at least 10, so trying to use `HOUR()' on shorter `TIMESTAMP' values produces a meaningless result. You can to some extent assign values of one date type to an object of a different date type. However, there may be some alteration of the value or loss of information: * If you assign a `DATE' value to a `DATETIME' or `TIMESTAMP' object, the time part of the resulting value is set to `'00:00:00'', because the `DATE' value contains no time information. * If you assign a `DATETIME' or `TIMESTAMP' value to a `DATE' object, the time part of the resulting value is deleted, because the `DATE' type stores no time information. * Remember that although `DATETIME', `DATE', and `TIMESTAMP' values all can be specified using the same set of formats, the types do not all have the same range of values. For example, `TIMESTAMP' values cannot be earlier than `1970' or later than `2037'. This means that a date such as `'1968-01-01'', while legal as a `DATETIME' or `DATE' value, is not a valid `TIMESTAMP' value and will be converted to `0' if assigned to such an object. Be aware of certain pitfalls when specifying date values: * The relaxed format allowed for values specified as strings can be deceiving. For example, a value such as `'10:11:12'' might look like a time value because of the `:' delimiter, but if used in a date context will be interpreted as the year `'2010-11-12''. The value `'10:45:15'' will be converted to `'0000-00-00'' because `'45'' is not a legal month. * Year values specified as two digits are ambiguous, because the century is unknown. *MySQL* interprets 2-digit year values using the following rules: - Year values in the range `00-69' are converted to `2000-2069'. - Year values in the range `70-99' are converted to `1970-1999'. The `TIME' Type ............... *MySQL* retrieves and displays `TIME' values in `'HH:MM:SS'' format (or `'HHH:MM:SS'' format for large hours values). `TIME' values may range from `'-838:59:59'' to `'838:59:59''. The reason the hours part may be so large is that the `TIME' type may be used not only to represent a time of day (which must be less than 24 hours), but also elapsed time or a time interval between two events (which may be much greater than 24 hours, or even negative). You can specify `TIME' values in a variety of formats: * As a string in `'D HH:MM:SS.fraction'' format. (Note that *MySQL* doesn't yet store the fraction for the time column). One can also use one of the following "relaxed" syntax: `HH:MM:SS.fraction', `HH:MM:SS', `HH:MM', `D HH:MM:SS', `D HH:MM', `D HH' or `SS'. Here `D' is days between 0-33. * As a string with no delimiters in `'HHMMSS'' format, provided that it makes sense as a time. For example, `'101112'' is understood as `'10:11:12'', but `'109712'' is illegal (it has a nonsensical minute part) and becomes `'00:00:00''. * As a number in `HHMMSS' format, provided that it makes sense as a time. For example, `101112' is understood as `'10:11:12''. The following alternative formats are also understood: `SS', `MMSS',`HHMMSS', `HHMMSS.fraction'. Note that *MySQL* doesn't yet store the fraction part. * As the result of a function that returns a value that is acceptable in a `TIME' context, such as `CURRENT_TIME'. For `TIME' values specified as strings that include a time part delimiter, it is not necessary to specify two digits for hours, minutes, or seconds values that are less than `10'. `'8:3:2'' is the same as `'08:03:02''. Be careful about assigning "short" `TIME' values to a `TIME' column. Without semicolon, *MySQL* interprets values using the assumption that the rightmost digits represent seconds. (*MySQL* interprets `TIME' values as elapsed time rather than as time of day.) For example, you might think of `'1112'' and `1112' as meaning `'11:12:00'' (12 minutes after 11 o'clock), but *MySQL* interprets them as `'00:11:12'' (11 minutes, 12 seconds). Similarly, `'12'' and `12' are interpreted as `'00:00:12''. `TIME' values with semicolon, instead, are always treated as time of the day. That is `'11:12'' will mean `'11:12:00'', not `'00:11:12''. Values that lie outside the `TIME' range but are otherwise legal are clipped to the appropriate endpoint of the range. For example, `'-850:00:00'' and `'850:00:00'' are converted to `'-838:59:59'' and `'838:59:59''. Illegal `TIME' values are converted to `'00:00:00''. Note that because `'00:00:00'' is itself a legal `TIME' value, there is no way to tell, from a value of `'00:00:00'' stored in a table, whether the original value was specified as `'00:00:00'' or whether it was illegal. The `YEAR' Type ............... The `YEAR' type is a 1-byte type used for representing years. *MySQL* retrieves and displays `YEAR' values in `YYYY' format. The range is `1901' to `2155'. You can specify `YEAR' values in a variety of formats: * As a four-digit string in the range `'1901'' to `'2155''. * As a four-digit number in the range `1901' to `2155'. * As a two-digit string in the range `'00'' to `'99''. Values in the ranges `'00'' to `'69'' and `'70'' to `'99'' are converted to `YEAR' values in the ranges `2000' to `2069' and `1970' to `1999'. * As a two-digit number in the range `1' to `99'. Values in the ranges `1' to `69' and `70' to `99' are converted to `YEAR' values in the ranges `2001' to `2069' and `1970' to `1999'. Note that the range for two-digit numbers is slightly different than the range for two-digit strings, because you cannot specify zero directly as a number and have it be interpreted as `2000'. You _must_ specify it as a string `'0'' or `'00'' or it will be interpreted as `0000'. * As the result of a function that returns a value that is acceptable in a `YEAR' context, such as `NOW()'. Illegal `YEAR' values are converted to `0000'. String Types ------------ The string types are `CHAR', `VARCHAR', `BLOB', `TEXT', `ENUM', and `SET'. This section describes how these types work, their storage requirements, and how to use them in your queries. The `CHAR' and `VARCHAR' Types .............................. The `CHAR' and `VARCHAR' types are similar, but differ in the way they are stored and retrieved. The length of a `CHAR' column is fixed to the length that you declare when you create the table. The length can be any value between 1 and 255. (As of *MySQL* Version 3.23, the length of `CHAR' may be 0 to 255.) When `CHAR' values are stored, they are right-padded with spaces to the specified length. When `CHAR' values are retrieved, trailing spaces are removed. Values in `VARCHAR' columns are variable-length strings. You can declare a `VARCHAR' column to be any length between 1 and 255, just as for `CHAR' columns. However, in contrast to `CHAR', `VARCHAR' values are stored using only as many characters as are needed, plus one byte to record the length. Values are not padded; instead, trailing spaces are removed when values are stored. (This space removal differs from the ANSI SQL specification.) If you assign a value to a `CHAR' or `VARCHAR' column that exceeds the column's maximum length, the value is truncated to fit. The table below illustrates the differences between the two types of columns by showing the result of storing various string values into `CHAR(4)' and `VARCHAR(4)' columns: *Value* `CHAR(4)' *Storage `VARCHAR(4)' *Storage required* required* `''' `' '' 4 bytes `''' 1 byte `'ab'' `'ab '' 4 bytes `'ab'' 3 bytes `'abcd'' `'abcd'' 4 bytes `'abcd'' 5 bytes `'abcdefgh'' `'abcd'' 4 bytes `'abcd'' 5 bytes The values retrieved from the `CHAR(4)' and `VARCHAR(4)' columns will be the same in each case, because trailing spaces are removed from `CHAR' columns upon retrieval. Values in `CHAR' and `VARCHAR' columns are sorted and compared in case-insensitive fashion, unless the `BINARY' attribute was specified when the table was created. The `BINARY' attribute means that column values are sorted and compared in case-sensitive fashion according to the ASCII order of the machine where the *MySQL* server is running. `BINARY' doesn't affect how the column is stored or retrieved. The `BINARY' attribute is sticky. This means that if a column marked `BINARY' is used in an expression, the whole expression is compared as a `BINARY' value. *MySQL* may silently change the type of a `CHAR' or `VARCHAR' column at table creation time. *Note Silent column changes::. The `BLOB' and `TEXT' Types ........................... A `BLOB' is a binary large object that can hold a variable amount of data. The four `BLOB' types `TINYBLOB', `BLOB', `MEDIUMBLOB', and `LONGBLOB' differ only in the maximum length of the values they can hold. *Note Storage requirements::. The four `TEXT' types `TINYTEXT', `TEXT', `MEDIUMTEXT', and `LONGTEXT' correspond to the four `BLOB' types and have the same maximum lengths and storage requirements. The only difference between `BLOB' and `TEXT' types is that sorting and comparison is performed in case-sensitive fashion for `BLOB' values and case-insensitive fashion for `TEXT' values. In other words, a `TEXT' is a case-insensitive `BLOB'. If you assign a value to a `BLOB' or `TEXT' column that exceeds the column type's maximum length, the value is truncated to fit. In most respects, you can regard a `TEXT' column as a `VARCHAR' column that can be as big as you like. Similarly, you can regard a `BLOB' column as a `VARCHAR BINARY' column. The differences are: * You can have indexes on `BLOB' and `TEXT' columns with *MySQL* Version 3.23.2 and newer. Older versions of *MySQL* did not support this. * There is no trailing-space removal for `BLOB' and `TEXT' columns when values are stored, as there is for `VARCHAR' columns. * `BLOB' and `TEXT' columns cannot have `DEFAULT' values. *MyODBC* defines `BLOB' values as `LONGVARBINARY' and `TEXT' values as `LONGVARCHAR'. Because `BLOB' and `TEXT' values may be extremely long, you may run up against some constraints when using them: * If you want to use `GROUP BY' or `ORDER BY' on a `BLOB' or `TEXT' column, you must convert the column value into a fixed-length object. The standard way to do this is with the `SUBSTRING' function. For example: mysql> select comment from tbl_name,substring(comment,20) as substr ORDER BY substr; If you don't do this, only the first `max_sort_length' bytes of the column are used when sorting. The default value of `max_sort_length' is 1024; this value can be changed using the `-O' option when starting the `mysqld' server. You can group on an expression involving `BLOB' or `TEXT' values by specifying the column position or by using an alias: mysql> select id,substring(blob_col,1,100) from tbl_name GROUP BY 2; mysql> select id,substring(blob_col,1,100) as b from tbl_name GROUP BY b; * The maximum size of a `BLOB' or `TEXT' object is determined by its type, but the largest value you can actually transmit between the client and server is determined by the amount of available memory and the size of the communications buffers. You can change the message buffer size, but you must do so on both the server and client ends. *Note Server parameters::. Note that each `BLOB' or `TEXT' value is represented internally by a separately allocated object. This is in contrast to all other column types, for which storage is allocated once per column when the table is opened. The `ENUM' Type ............... An `ENUM' is a string object whose value normally is chosen from a list of allowed values that are enumerated explicitly in the column specification at table creation time. The value may also be the empty string (`""') or `NULL' under certain circumstances: * If you insert an invalid value into an `ENUM' (that is, a string not present in the list of allowed values), the empty string is inserted instead as a special error value. * If an `ENUM' is declared `NULL', `NULL' is also a legal value for the column, and the default value is `NULL'. If an `ENUM' is declared `NOT NULL', the default value is the first element of the list of allowed values. Each enumeration value has an index: * Values from the list of allowable elements in the column specification are numbered beginning with 1. * The index value of the empty string error value is 0. This means that you can use the following `SELECT' statement to find rows into which invalid `ENUM' values were assigned: mysql> SELECT * FROM tbl_name WHERE enum_col=0; * The index of the `NULL' value is `NULL'. For example, a column specified as `ENUM("one", "two", "three")' can have any of the values shown below. The index of each value is also shown: *Value* *Index* `NULL' `NULL' `""' 0 `"one"' 1 `"two"' 2 `"three"' 3 An enumeration can have a maximum of 65535 elements. Lettercase is irrelevant when you assign values to an `ENUM' column. However, values retrieved from the column later have lettercase matching the values that were used to specify the allowable values at table creation time. If you retrieve an `ENUM' in a numeric context, the column value's index is returned. For example, you can retrieve numeric values from an `ENUM' column like this: mysql> SELECT enum_col+0 FROM tbl_name; If you store a number into an `ENUM', the number is treated as an index, and the value stored is the enumeration member with that index. (However, this will not work with `LOAD DATA', which treats all input as strings.) `ENUM' values are sorted according to the order in which the enumeration members were listed in the column specification. (In other words, `ENUM' values are sorted according to their index numbers.) For example, `"a"' sorts before `"b"' for `ENUM("a", "b")', but `"b"' sorts before `"a"' for `ENUM("b", "a")'. The empty string sorts before non-empty strings, and `NULL' values sort before all other enumeration values. If you want to get all possible values for an `ENUM' column, you should use: `SHOW COLUMNS FROM table_name LIKE enum_column_name' and parse the `ENUM' definition in the second column. The `SET' Type .............. A `SET' is a string object that can have zero or more values, each of which must be chosen from a list of allowed values specified when the table is created. `SET' column values that consist of multiple set members are specified with members separated by commas (`,'). A consequence of this is that `SET' member values cannot themselves contain commas. For example, a column specified as `SET("one", "two") NOT NULL' can have any of these values: "" "one" "two" "one,two" A `SET' can have a maximum of 64 different members. *MySQL* stores `SET' values numerically, with the low-order bit of the stored value corresponding to the first set member. If you retrieve a `SET' value in a numeric context, the value retrieved has bits set corresponding to the set members that make up the column value. For example, you can retrieve numeric values from a `SET' column like this: mysql> SELECT set_col+0 FROM tbl_name; If a number is stored into a `SET' column, the bits that are set in the binary representation of the number determine the set members in the column value. Suppose a column is specified as `SET("a","b","c","d")'. Then the members have the following bit values: `SET' *Decimal *Binary value* *member* value* `a' `1' `0001' `b' `2' `0010' `c' `4' `0100' `d' `8' `1000' If you assign a value of `9' to this column, that is `1001' in binary, so the first and fourth `SET' value members `"a"' and `"d"' are selected and the resulting value is `"a,d"'. For a value containing more than one `SET' element, it does not matter what order the elements are listed in when you insert the value. It also does not matter how many times a given element is listed in the value. When the value is retrieved later, each element in the value will appear once, with elements listed according to the order in which they were specified at table creation time. For example, if a column is specified as `SET("a","b","c","d")', then `"a,d"', `"d,a"', and `"d,a,a,d,d"' will all appear as `"a,d"' when retrieved. `SET' values are sorted numerically. `NULL' values sort before non-`NULL' `SET' values. Normally, you perform a `SELECT' on a `SET' column using the `LIKE' operator or the `FIND_IN_SET()' function: mysql> SELECT * FROM tbl_name WHERE set_col LIKE '%value%'; mysql> SELECT * FROM tbl_name WHERE FIND_IN_SET('value',set_col)>0; But the following will also work: mysql> SELECT * FROM tbl_name WHERE set_col = 'val1,val2'; mysql> SELECT * FROM tbl_name WHERE set_col & 1; The first of these statements looks for an exact match. The second looks for values containing the first set member. If you want to get all possible values for a `SET' column, you should use: `SHOW COLUMNS FROM table_name LIKE set_column_name' and parse the `SET' definition in the second column. Choosing the Right Type for a Column ------------------------------------ For the most efficient use of storage, try to use the most precise type in all cases. For example, if an integer column will be used for values in the range between `1' and `99999', `MEDIUMINT UNSIGNED' is the best type. Accurate representation of monetary values is a common problem. In *MySQL*, you should use the `DECIMAL' type. This is stored as a string, so no loss of accuracy should occur. If accuracy is not too important, the `DOUBLE' type may also be good enough. For high precision, you can always convert to a fixed-point type stored in a `BIGINT'. This allows you to do all calculations with integers and convert results back to floating-point values only when necessary. Column Indexes -------------- All *MySQL* column types can be indexed. Use of indexes on the relevant columns is the best way to improve the performance of `SELECT' operations. The maximum number of keys and the maximum index length is defined per table handler. *Note Table types::. You can with all table handlers have at least 16 keys and a total index length of at least 256 bytes. For `CHAR' and `VARCHAR' columns, you can index a prefix of a column. This is much faster and requires less disk space than indexing the whole column. The syntax to use in the `CREATE TABLE' statement to index a column prefix looks like this: KEY index_name (col_name(length)) The example below creates an index for the first 10 characters of the `name' column: mysql> CREATE TABLE test ( name CHAR(200) NOT NULL, KEY index_name (name(10))); For `BLOB' and `TEXT' columns, you must index a prefix of the column. You cannot index the entire column. In *MySQL* Version 3.23.23 or later, you can also create special *FULLTEXT* indexes. They are used for full-text search. Only the `MyISAM' table type supports `FULLTEXT' indexes. They can be created only from `VARCHAR' and `TEXT' columns. Indexing always happens over the entire column and partial indexing is not supported. See *Note Fulltext Search:: for details. Multiple-column Indexes ----------------------- *MySQL* can create indexes on multiple columns. An index may consist of up to 15 columns. (On `CHAR' and `VARCHAR' columns you can also use a prefix of the column as a part of an index). A multiple-column index can be considered a sorted array containing values that are created by concatenating the values of the indexed columns. *MySQL* uses multiple-column indexes in such a way that queries are fast when you specify a known quantity for the first column of the index in a `WHERE' clause, even if you don't specify values for the other columns. Suppose a table is created using the following specification: mysql> CREATE TABLE test ( id INT NOT NULL, last_name CHAR(30) NOT NULL, first_name CHAR(30) NOT NULL, PRIMARY KEY (id), INDEX name (last_name,first_name)); Then the index `name' is an index over `last_name' and `first_name'. The index will be used for queries that specify values in a known range for `last_name', or for both `last_name' and `first_name'. Therefore, the `name' index will be used in the following queries: mysql> SELECT * FROM test WHERE last_name="Widenius"; mysql> SELECT * FROM test WHERE last_name="Widenius" AND first_name="Michael"; mysql> SELECT * FROM test WHERE last_name="Widenius" AND (first_name="Michael" OR first_name="Monty"); mysql> SELECT * FROM test WHERE last_name="Widenius" AND first_name >="M" AND first_name < "N"; However, the `name' index will NOT be used in the following queries: mysql> SELECT * FROM test WHERE first_name="Michael"; mysql> SELECT * FROM test WHERE last_name="Widenius" OR first_name="Michael"; For more information on the manner in which *MySQL* uses indexes to improve query performance, see *Note *MySQL* indexes: MySQL indexes. Using Column Types from Other Database Engines ---------------------------------------------- To make it easier to use code written for SQL implementations from other vendors, *MySQL* maps column types as shown in the table below. These mappings make it easier to move table definitions from other database engines to *MySQL*: *Other vendor type* *MySQL type* `BINARY(NUM)' `CHAR(NUM) BINARY' `CHAR VARYING(NUM)' `VARCHAR(NUM)' `FLOAT4' `FLOAT' `FLOAT8' `DOUBLE' `INT1' `TINYINT' `INT2' `SMALLINT' `INT3' `MEDIUMINT' `INT4' `INT' `INT8' `BIGINT' `LONG VARBINARY' `MEDIUMBLOB' `LONG VARCHAR' `MEDIUMTEXT' `MIDDLEINT' `MEDIUMINT' `VARBINARY(NUM)' `VARCHAR(NUM) BINARY' Column type mapping occurs at table creation time. If you create a table with types used by other vendors and then issue a `DESCRIBE tbl_name' statement, *MySQL* reports the table structure using the equivalent *MySQL* types. Functions for Use in `SELECT' and `WHERE' Clauses ================================================= A `select_expression' or `where_definition' in a SQL statement can consist of any expression using the functions described below. An expression that contains `NULL' always produces a `NULL' value unless otherwise indicated in the documentation for the operators and functions involved in the expression. *NOTE:* There must be no whitespace between a function name and the parenthesis following it. This helps the *MySQL* parser distinguish between function calls and references to tables or columns that happen to have the same name as a function. Spaces around arguments are permitted, though. You can force *MySQL* to accept spaces after the function name by starting `mysqld' with `--ansi' or using the `CLIENT_IGNORE_SPACE' to `mysql_connect()', but in this case all function names will become reserved words. *Note ANSI mode::. For the sake of brevity, examples display the output from the `mysql' program in abbreviated form. So this: mysql> select MOD(29,9); 1 rows in set (0.00 sec) +-----------+ | mod(29,9) | +-----------+ | 2 | +-----------+ is displayed like this: mysql> select MOD(29,9); -> 2 Grouping Functions ------------------ `( ... )' Parentheses. Use these to force the order of evaluation in an expression: mysql> select 1+2*3; -> 7 mysql> select (1+2)*3; -> 9 Normal Arithmetic Operations ---------------------------- The usual arithmetic operators are available. Note that in the case of `-', `+', and `*', the result is calculated with `BIGINT' (64-bit) precision if both arguments are integers! `+' Addition: mysql> select 3+5; -> 8 `-' Subtraction: mysql> select 3-5; -> -2 `*' Multiplication: mysql> select 3*5; -> 15 mysql> select 18014398509481984*18014398509481984.0; -> 324518553658426726783156020576256.0 mysql> select 18014398509481984*18014398509481984; -> 0 The result of the last expression is incorrect because the result of the integer multiplication exceeds the 64-bit range of `BIGINT' calculations. `/' Division: mysql> select 3/5; -> 0.60 Division by zero produces a `NULL' result: mysql> select 102/(1-1); -> NULL A division will be calculated with `BIGINT' arithmetic only if performed in a context where its result is converted to an integer! Bit Functions ------------- *MySQL* uses `BIGINT' (64-bit) arithmetic for bit operations, so these operators have a maximum range of 64 bits. `|' Bitwise OR: mysql> select 29 | 15; -> 31 `&' Bitwise AND: mysql> select 29 & 15; -> 13 `<<' Shifts a longlong (`BIGINT') number to the left: mysql> select 1 << 2; -> 4 `>>' Shifts a longlong (`BIGINT') number to the right: mysql> select 4 >> 2; -> 1 `~' Invert all bits: mysql> select 5 & ~1; -> 4 `BIT_COUNT(N)' Returns the number of bits that are set in the argument `N': mysql> select BIT_COUNT(29); -> 4 Logical Operations ------------------ All logical functions return `1' (TRUE), `0' (FALSE) or `NULL' (unknown, which is in most cases the same as FALSE): `NOT' `!' Logical NOT. Returns `1' if the argument is `0', otherwise returns `0'. Exception: `NOT NULL' returns `NULL': mysql> select NOT 1; -> 0 mysql> select NOT NULL; -> NULL mysql> select ! (1+1); -> 0 mysql> select ! 1+1; -> 1 The last example returns `1' because the expression evaluates the same way as `(!1)+1'. `OR' `||' Logical OR. Returns `1' if either argument is not `0' and not `NULL': mysql> select 1 || 0; -> 1 mysql> select 0 || 0; -> 0 mysql> select 1 || NULL; -> 1 `AND' `&&' Logical AND. Returns `0' if either argument is `0' or `NULL', otherwise returns `1': mysql> select 1 && NULL; -> 0 mysql> select 1 && 0; -> 0 Comparison Operators -------------------- Comparison operations result in a value of `1' (TRUE), `0' (FALSE), or `NULL'. These functions work for both numbers and strings. Strings are automatically converted to numbers and numbers to strings as needed (as in Perl). *MySQL* performs comparisons using the following rules: * If one or both arguments are `NULL', the result of the comparison is `NULL', except for the `<=>' operator. * If both arguments in a comparison operation are strings, they are compared as strings. * If both arguments are integers, they are compared as integers. * Hexadecimal values are treated as binary strings if not compared to a number. * If one of the arguments is a `TIMESTAMP' or `DATETIME' column and the other argument is a constant, the constant is converted to a timestamp before the comparison is performed. This is done to be more ODBC-friendly. * In all other cases, the arguments are compared as floating-point (real) numbers. By default, string comparisons are done in case-independent fashion using the current character set (ISO-8859-1 Latin1 by default, which also works excellently for English). The examples below illustrate conversion of strings to numbers for comparison operations: mysql> SELECT 1 > '6x'; -> 0 mysql> SELECT 7 > '6x'; -> 1 mysql> SELECT 0 > 'x6'; -> 0 mysql> SELECT 0 = 'x6'; -> 1 `=' Equal: mysql> select 1 = 0; -> 0 mysql> select '0' = 0; -> 1 mysql> select '0.0' = 0; -> 1 mysql> select '0.01' = 0; -> 0 mysql> select '.01' = 0.01; -> 1 `<>' `!=' Not equal: mysql> select '.01' <> '0.01'; -> 1 mysql> select .01 <> '0.01'; -> 0 mysql> select 'zapp' <> 'zappp'; -> 1 `<=' Less than or equal: mysql> select 0.1 <= 2; -> 1 `<' Less than: mysql> select 2 <= 2; -> 1 `>=' Greater than or equal: mysql> select 2 >= 2; -> 1 `>' Greater than: mysql> select 2 > 2; -> 0 `<=>' Null safe equal: mysql> select 1 <=> 1, NULL <=> NULL, 1 <=> NULL; -> 1 1 0 `IS NULL' `IS NOT NULL' Test whether or not a value is or is not `NULL': mysql> select 1 IS NULL, 0 IS NULL, NULL IS NULL; -> 0 0 1 mysql> select 1 IS NOT NULL, 0 IS NOT NULL, NULL IS NOT NULL; -> 1 1 0 `expr BETWEEN min AND max' If `expr' is greater than or equal to `min' and `expr' is less than or equal to `max', `BETWEEN' returns `1', otherwise it returns `0'. This is equivalent to the expression `(min <= expr AND expr <= max)' if all the arguments are of the same type. The first argument (`expr') determines how the comparison is performed as follows: * If `expr' is a `TIMESTAMP', `DATE', or `DATETIME' column, `MIN()' and `MAX()' are formatted to the same format if they are constants. * If `expr' is a case-insensitive string expression, a case-insensitive string comparison is done. * If `expr' is a case-sensitive string expression, a case-sensitive string comparison is done. * If `expr' is an integer expression, an integer comparison is done. * Otherwise, a floating-point (real) comparison is done. mysql> select 1 BETWEEN 2 AND 3; -> 0 mysql> select 'b' BETWEEN 'a' AND 'c'; -> 1 mysql> select 2 BETWEEN 2 AND '3'; -> 1 mysql> select 2 BETWEEN 2 AND 'x-3'; -> 0 `expr IN (value,...)' Returns `1' if `expr' is any of the values in the `IN' list, else returns `0'. If all values are constants, then all values are evaluated according to the type of `expr' and sorted. The search for the item is then done using a binary search. This means `IN' is very quick if the `IN' value list consists entirely of constants. If `expr' is a case-sensitive string expression, the string comparison is performed in case-sensitive fashion: mysql> select 2 IN (0,3,5,'wefwf'); -> 0 mysql> select 'wefwf' IN (0,3,5,'wefwf'); -> 1 `expr NOT IN (value,...)' Same as `NOT (expr IN (value,...))'. `ISNULL(expr)' If `expr' is `NULL', `ISNULL()' returns `1', otherwise it returns `0': mysql> select ISNULL(1+1); -> 0 mysql> select ISNULL(1/0); -> 1 Note that a comparison of `NULL' values using `=' will always be false! `COALESCE(list)' Returns first non-`NULL' element in list: mysql> select COALESCE(NULL,1); -> 1 mysql> select COALESCE(NULL,NULL,NULL); -> NULL `INTERVAL(N,N1,N2,N3,...)' Returns `0' if `N' < `N1', `1' if `N' < `N2' and so on. All arguments are treated as integers. It is required that `N1' < `N2' < `N3' < `...' < `Nn' for this function to work correctly. This is because a binary search is used (very fast): mysql> select INTERVAL(23, 1, 15, 17, 30, 44, 200); -> 3 mysql> select INTERVAL(10, 1, 10, 100, 1000); -> 2 mysql> select INTERVAL(22, 23, 30, 44, 200); -> 0 String Comparison Functions --------------------------- Normally, if any expression in a string comparison is case sensitive, the comparison is performed in case-sensitive fashion. `expr LIKE pat [ESCAPE 'escape-char']' Pattern matching using SQL simple regular expression comparison. Returns `1' (TRUE) or `0' (FALSE). With `LIKE' you can use the following two wild-card characters in the pattern: `%' Matches any number of characters, even zero characters `_' Matches exactly one character mysql> select 'David!' LIKE 'David_'; -> 1 mysql> select 'David!' LIKE '%D%v%'; -> 1 To test for literal instances of a wild-card character, precede the character with the escape character. If you don't specify the `ESCAPE' character, `\' is assumed: `\%' Matches one `%' character `\_' Matches one `_' character mysql> select 'David!' LIKE 'David\_'; -> 0 mysql> select 'David_' LIKE 'David\_'; -> 1 To specify a different escape character, use the `ESCAPE' clause: mysql> select 'David_' LIKE 'David|_' ESCAPE '|'; -> 1 `LIKE' is allowed on numeric expressions! (This is a *MySQL* extension to the ANSI SQL `LIKE'.) mysql> select 10 LIKE '1%'; -> 1 Note: Because *MySQL* uses the C escape syntax in strings (for example, `\n'), you must double any `\' that you use in your `LIKE' strings. For example, to search for `\n', specify it as `\\n'. To search for `\', specify it as `\\\\' (the backslashes are stripped once by the parser and another time when the pattern match is done, leaving a single backslash to be matched). `expr NOT LIKE pat [ESCAPE 'escape-char']' Same as `NOT (expr LIKE pat [ESCAPE 'escape-char'])'. `expr REGEXP pat' `expr RLIKE pat' Performs a pattern match of a string expression `expr' against a pattern `pat'. The pattern can be an extended regular expression. *Note Regexp::. Returns `1' if `expr' matches `pat', otherwise returns `0'. `RLIKE' is a synonym for `REGEXP', provided for `mSQL' compatibility. Note: Because *MySQL* uses the C escape syntax in strings (for example, `\n'), you must double any `\' that you use in your `REGEXP' strings. As of *MySQL* Version 3.23.4, `REGEXP' is case insensitive for normal (not binary) strings: mysql> select 'Monty!' REGEXP 'm%y%%'; -> 0 mysql> select 'Monty!' REGEXP '.*'; -> 1 mysql> select 'new*\n*line' REGEXP 'new\\*.\\*line'; -> 1 mysql> select "a" REGEXP "A", "a" REGEXP BINARY "A"; -> 1 0 mysql> select "a" REGEXP "^[a-d]"; -> 1 `' `REGEXP' and `RLIKE' use the current character set (ISO-8859-1 Latin1 by default) when deciding the type of a character. `expr NOT REGEXP pat' `expr NOT RLIKE pat' Same as `NOT (expr REGEXP pat)'. `STRCMP(expr1,expr2)' `STRCMP()' returns `0' if the strings are the same, `-1' if the first argument is smaller than the second according to the current sort order, and `1' otherwise: mysql> select STRCMP('text', 'text2'); -> -1 mysql> select STRCMP('text2', 'text'); -> 1 mysql> select STRCMP('text', 'text'); -> 0 `MATCH (col1,col2,...) AGAINST (expr)' `MATCH ... AGAINST()' is used for full-text search and returns relevance - similarity measure between the text in columns `(col1,col2,...)' and the query `expr'. Relevance is a positive floating-point number. Zero relevance means no similarity. For `MATCH ... AGAINST()' to work, a *FULLTEXT* index must be created first. *Note `CREATE TABLE': CREATE TABLE. `MATCH ... AGAINST()' is available in *MySQL* Version 3.23.23 or later. For details and usage examples *note Fulltext Search::. Cast Operators -------------- ``BINARY'' The `BINARY' operator casts the string following it to a binary string. This is an easy way to force a column comparison to be case sensitive even if the column isn't defined as `BINARY' or `BLOB': mysql> select "a" = "A"; -> 1 mysql> select BINARY "a" = "A"; -> 0 `BINARY' was introduced in *MySQL* Version 3.23.0. Note that in some context *MySQL* will not be able to use the index efficiently when you cast an indexed column to `BINARY'. If you want to compare a blob case-insensitively you can always convert the blob to upper case before doing the comparison: SELECT 'A' LIKE UPPER(blob_col) FROM table_name; We plan to soon introduce casting between different character sets to make string comparison even more flexible. Control Flow Functions ---------------------- `IFNULL(expr1,expr2)' If `expr1' is not `NULL', `IFNULL()' returns `expr1', else it returns `expr2'. `IFNULL()' returns a numeric or string value, depending on the context in which it is used: mysql> select IFNULL(1,0); -> 1 mysql> select IFNULL(NULL,10); -> 10 mysql> select IFNULL(1/0,10); -> 10 mysql> select IFNULL(1/0,'yes'); -> 'yes' `NULLIF(expr1,expr2)' If `expr1 = expr2' is true, return `NULL' else return `expr1'. This is the same as `CASE WHEN x = y THEN NULL ELSE x END': mysql> select NULLIF(1,1); -> NULL mysql> select NULLIF(1,2); -> 1 Note that `expr1' is evaluated twice in *MySQL* if the arguments are equal. `IF(expr1,expr2,expr3)' If `expr1' is TRUE (`expr1 <> 0' and `expr1 <> NULL') then `IF()' returns `expr2', else it returns `expr3'. `IF()' returns a numeric or string value, depending on the context in which it is used: mysql> select IF(1>2,2,3); -> 3 mysql> select IF(1<2,'yes','no'); -> 'yes' mysql> select IF(strcmp('test','test1'),'no','yes'); -> 'no' `expr1' is evaluated as an integer value, which means that if you are testing floating-point or string values, you should do so using a comparison operation: mysql> select IF(0.1,1,0); -> 0 mysql> select IF(0.1<>0,1,0); -> 1 In the first case above, `IF(0.1)' returns `0' because `0.1' is converted to an integer value, resulting in a test of `IF(0)'. This may not be what you expect. In the second case, the comparison tests the original floating-point value to see whether it is non-zero. The result of the comparison is us