MySQL is used in over 4 million installations all over the world. It is licensed under both GNU GPL (General Public License) and commercial licenses, depending upon what level of support that you require. It has a large user community, which makes it somewhat easier to use under the GPL license. There are actually four versions of MySQL:
MySQL Standard includes the standard storage engine, as well as the InnoDB storage engine, which is touted as a "transaction-safe, ACID-compliant database" with some additional features over the standard version.
MySQL Pro is the commercial version.
MySQL Max includes the more technologically advanced features that are available during early access programs.
MySQL Classic is the standard storage engine without the InnoDB engine. This is another commercial version.
Most of the recommendations discussed in this article apply to all versions of MySQL unless otherwise noted.
Distinguishing features
The following features are implemented by MySQL:
Multiple storage engines, allowing you to choose the one which is most effective for each table in the application (in MySQL 5.0, storage engines must be compiled in; in MySQL 5.1, storage engines can be dynamically loaded at run time):
