There are four versions of the database server available:

MySQL Standard includes the standard MySQL storage engines and the InnoDB storage engine. InnoDB is a transaction-safe, ACID-compliant storage engine with commit, rollback, crash recovery and row-level locking capabilities. This version is for users who want the high-performance MySQL database with full transaction support. MySQL Standard is licensed under the GPL. MySQL Pro is the commercially-licensed version of the server with the same feature-set.

MySQL Max is for the user who wants early access to new features. This version includes the standard MySQL storage engines, the InnoDB storage engine, and other extras like the Berkeley database (BDB) storage engine, and support for splitting tables across multiple files to avoid operating system file size limitations. In future releases, MySQL Max will include more cutting-edge features.

MySQL Pro is the commercially licensed version of the MySQL Standard database server, including InnoDB support.

MySQL Classic only includes the standard MySQL storage engines, differing from MySQL Pro and MySQL Standard only by the omission of the InnoDB storage engine. It is only available under a commercial license.

Features:

ANSI SQL syntax support :

The MySQL database server supports a broad subset of the ANSI SQL 99 syntax, along with extra extensions such as the REPLACE statement and the LIMIT clause for SELECT and DELETE. Alternative syntaxes from other database systems are also supported, to make porting applications easier. The coverage of the complete ANSI SQL 99 syntax is expanding, with version 4.0 introducing support for the UNION statement.

Cross-platform support :

We provide optimized binaries for a wide range of platforms, including Linux, Microsoft Windows, FreeBSD, Sun Solaris, IBM's AIX, Mac OS X, HP-UX, AIX, QNX, Novell NetWare, SCO Open UNIX, SGI Irix, and Dec OSF.

You can connect to a MySQL database server from all of the major platforms, using nearly any programming language, with our standard thread safe client library or one of the products in our Connector family of database drivers.

Independent storage engines:

 
MySQL database server's unique independent storage engines let you choose the type of database storage that is most appropriate for your particular needs. If you need row-level locking and transaction support, you can use the InnoDB storage engine. If your application doesn't require transactions, you can use the MyISAM storage engine for maximum performance.

Transactions:

 
Using the InnoDB or Berkeley DB (BDB) storage engines, the MySQL database server supports transactions. The InnoDB storage engine also supports foreign key constraints.

Flexible security system, including SSL support :

The MySQL database server has an advanced permissions and security system, including support for SSL transport-layer encryption. As of version 4.0, the security system also allows you to limit server resources on a per-user basis.

Query caching :

Version 4.0 of the server includes a new query cache, which can significantly increase the performance of commonly-issued queries, without requiring any special programming. Performance can be increased by over 200% in typical usage.

Replication:

 
Using database replication, you can have many "slave" servers running off a single "master" server for robustness and speed.

Full-text indexing and searching :

Full-text indexes allow you to search fields containing arbitrary text for specific words and phrases, including relevance rankings. With version 4.0, we've expanded the full text search to include exact phrase matching and Boolean search operators, which allows for even more fine-grained control over your search results.

Embedded database library :

Using the embedded database library (libmysqld), you can include the full power of the MySQL database server into applications and electronics devices, without your end-user having any awareness of the underlying database. The embedded MySQL database is ideal for use behind the scenes in Internet appliances, public kiosks, turn-key hardware/software combination units, high performance Internet servers, self-contained databases distributed on CD-ROM, and more possibilities just waiting for you to invent them.

Upcoming Features:

Character set handling, with full Unicode support:

 
While earlier versions of the database server can be set up to support specific characters sets, version 4.1 adds support for multiple character sets which can be set at the server, database, table, or field level, as well as improved support for converting between character sets. New character sets have been added for storing Unicode data in the UCS2 and UTF8 encodings.

Expanded support for sub queries:

 
Sub queries allow you to use the result of one query as a component of a larger query. The MySQL server already supports some forms of this technique, such as INSERT INTO ... SELECT ..., and this support will be expanded in version 4.1 to include nested SELECT queries, which is one of the most-requested features from our users.

GIS (Geometrical data):

 
Version 4.1 includes support for a subset of the SQL92 with Geometry Types environment proposed by the Open GIS Consortium. This allows for efficiently storing and manipulating spatial data, including geographic data.

Multi-master replication :

Multi-master replication will allow for a slave database server to track data in multiple master databases. Support for this feature will be included in version 5.0.

Stored procedures and triggers:

Stored procedures allow you to create functions and subroutines that run on the server. This makes it possible to grant access to specific queries without granting carte blanche access to the underlying data, or validate data in the database before it is stored. Triggers can be configured to fire when certain conditions are fulfilled. The MySQL database server will provide hooks for implementing stored procedures in multiple languages, as well as including support for the Persistent Stored Modules syntax defined as part of ANSI SQL-99.Support for stored procedures and triggers will be introduced in version 5.0.

Views:

 
Views allow you to configure alternative views of existing tables without changing the underlying table structure. They can be used to grant limited access to tables, or make it easier to construct certain types of queries. Views are currently scheduled to be supported in version 5.1.