MySQL Manual | D.3 Changes in release 4.0.x (Production)

D.3 Changes in release 4.0.x (Production)

Version 4.0 of the MySQL server includes many enhancements and new features:

The InnoDB table type is now included in the standard binaries, adding transactions, row-level locking, and foreign keys. See section 7.5 InnoDB Tables.
A query cache, offering vastly increased performance for many applications. By caching complete result sets, later identical queries can return instantly. See section 6.9 MySQL Query Cache.
Improved full-text indexing with boolean mode, truncation, and phrase searching. See section 6.8 MySQL Full-text Search.
Enhanced MERGE tables, now supporting INSERT statements and AUTO_INCREMENT. See section 7.2 MERGE Tables.
UNION syntax in SELECT. See section 6.4.1.2 UNION Syntax.
Multi-table DELETE statements. See section 6.4.6 DELETE Syntax.
libmysqld, the embedded server library. See section 9.1.15 libmysqld, the Embedded MySQL Server Library.
Additional GRANT privilege options for even tighter control and security. See section 4.3.1 GRANT and REVOKE Syntax.
Management of user resources in the GRANT system, particularly useful for ISPs and other hosting providers. See section 4.3.6 Limiting user resources.
Dynamic server variables, allowing configuration changes without having to take down the server. See section 5.5.6 SET Syntax.
Improved replication code and features. See section 4.10 Replication in MySQL.
Numerous new functions and options.
Changes to existing code for enhanced performance and reliability.

For a full list of changes, please refer to the changelog sections for each individual 4.0.x release.