The InnoDB storage engine is now included in the standard binaries, adding transactions, row-level locking, and foreign keys. See Section 13.2, “The InnoDB Storage Engine”.

A query cache, offering vastly increased performance for many applications. By caching complete result sets, later identical queries can return instantly. See Section 7.5.4, “The MySQL Query Cache”.

Improved full-text indexing with boolean mode, truncation, and phrase searching. See Section 11.8, “Full-Text Search Functions”.

Enhanced MERGE tables, now supporting INSERT statements and AUTO_INCREMENT. See Section 13.3, “The MERGE Storage Engine”.

UNION syntax in SELECT. See Section 12.2.7.3, “UNION Syntax”.

Multiple-table DELETE statements. See Section 12.2.1, “DELETE Syntax”.

libmysqld, the embedded server library. See Section 17.5, “libmysqld, the Embedded MySQL Server Library”.

Additional GRANT privilege options for even tighter control and security. See Section 12.4.1.2, “GRANT Syntax”.

Management of user resources in the GRANT system, particularly useful for ISPs and other hosting providers. See Section 5.6.4, “Setting Account Resource Limits”.

Dynamic server variables, allowing configuration changes to be made without having to stop and restart the server. See Section 12.4.4, “SET Syntax”.

Improved replication code and features. See Chapter 14, Replication.

Numerous new functions and options.

Changes to existing code for enhanced performance and reliability.