Via Matt, via OSNews, a slightly old article (though the information is still current) at Linux Magazine by Jeremy Zawodny about new features in MySQL 4.0. Of course, I'm most looking forward to 4.1 (we'll finally have sub-selects), but 4.0 has unions, InnoDB tables, transactions, and a "query cache" which sounds like it has the possibility of significantly speeding up sites that run the same queries all the time. It sounds like they did a lot of refactoring in general too.
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