Don't believe what you hear about MySQL. MySQL is great for simple PHP web applications, but not for more advanced applications. Don't expect version 5.0 to hit production status anytime soon. Version 4.1, which finally introdces subqueries and added functions still isn't even production yet. If you need stored procedures, subqueries, views, foreign keys, transactions, triggers, etc, MySQL is not for you. InnoDB supports FK and transactions, but that's it. PostgreSQL is a much better database, has the most features out of the open source databases, and is more similar to Oracle. It supports numerous languages for writing code, with the default PL/pgSQL very similar to Oracle's PL/SQL. Firebird is another feature-rich open source database. PostgreSQL FireBird