* MySQL 4.0: This version is the old stable release and hardly any MySQL web hosting provider uses them. Though new releases are issued, they only help to fix extremely critical bugs. Some of the features of MySQL 4.0 include MySQL server library, the transactional engine InnoDB and other features that help to simplify migration to MySQL from other databases.
* MySQL 4.1: This stable release has been followed by several new releases so as to fix the critical bugs and other security problems. The features of this series include sub-queries, Unicode support, faster binary client/ server protocol, Create Table, MyISAM storage engine, Archive storage engine, Blackhole storage engine and many more.
* MySQL 5.0: This is the current stable release that follows the SQL: 2003 syntax. This MySQL web hosting can even return multiple result sets in a single invocation. New releases are also issued to fix the bugs.