From Wikipedia, the free encyclopedia.
MySQL is a computer software product, a multithreadeded, multi-user, SQL (Structured Query Language) relational database server. MySQL, as free software, utilises the GNU General Public License. The PHP-MySQL combination is also cross-platform.
The Swedish company MySQL AB writes and maintains the system, selling support and service contracts, as well as commercially-licensed copies of MySQL, and employing people all over the world who communicate over the internet. Two Swedes and a Finn founded MySQL AB: David Axmark, Allan Larsson and Michael "Monty" Widenius. Despite the widespread pronunciation of "SQL" as "sequel," professionals generally pronounce "MySQL" as "my ess-que-ell," not "my-sequel."
MySQL, an open source product, works on many different platforms—including AIX, BSDi, FreeBSD, HP-UX, Linux, Mac OS X, NetBSD, OpenBSD, OS/2 Warp, SGI IRIX, Solaris, SunOS, SCO OpenServer, SCO UnixWare, Tru64, Windows 95, Windows 98, Windows NT, Windows 2000, Windows XP, and more recent versions of Windows.
Programming languages—which can access MySQL databases—include C, C++, Eiffel, Java, Perl, PHP, Python, Ruby, and Tcl; each of these using a specific API. An ODBC interface called MyODBC also exists which allows additional programming languages that support the ODBC interface to communicate with a MySQL. MySQL uses ANSI C as its "native" language.
MySQL is popular for web applications and acts as the database component of LAMP.
- A broad subset of ANSI SQL 99, as well as extensions
- Cross-platform support
- Independent storage engines (MyISAM for read speed, InnoDB for transactions and referential integrity)
- SSL Support
- Query caching
- Full-text indexing and searching
- Embedded database library
The development versionAs of 2003, the development version, Version 4.1, includes support for the following features:
- Support for geographical data (OpenGIS)
- Derived tables
- Multi-line queries
Future releasesMySQL 5.0 will contain support for the following features:
- Stored procedures
- True VARCHAR support
- Easier GIS access
- Foreign key support for all table types
- Online backup
- Fail-safe replication
- Column-level constraints
Criticisms of MySQL
Early versions of MySQL included few standard DBMS features, and the current production version still lacks many properties found in other SQL DBMSes. This has led some database experts, such as Chris Date and Fabian Pascal, to criticize MySQL as falling short of being a DBMS. 
Many of the early criticisms have been remedied in later versions of the software, including the lack of transactions and relational integrity constraints. These are features necessary to support the "ACID properties" for relational databases, which allow the DBMS to ensure that client applications cannot interfere with one another or insert inconsistent values.  Other criticisms include MySQL's divergence from the SQL standard on the subject of treatment of NULL values and default values. 
Critics find MySQL's popularity surprising in the light of the existence of other open-source database projects with comparable performance and in closer compliance to the SQL standards. MySQL advocates reply that the program serves its purpose for its users, who are willing to accept the program's limitations (which decrease with every major revision) in exchange for speed, simplicity, and rapid development.
Wikipedia on MySQL
In August 2001, a test version of the Wikipedia software using PHP and MySQL appeared; in January 2002 it became the new software running Wikipedia. See the MediaWiki page. In May 2003, this code base underwent an upgrade to MySQL version 4.0.12 from the previous version 3.x.