>I am interested in learning, and perhaps applying, Client-Server. Is MySQL recommended for this? Any serious limitations compared to more expensive systems, like Oracle or Microsoft SQL Server?

MySQL lacks transactions and stored procs (until v4, at least).

PostgreSQL, on the other hand, is also free and has those features. For a project I'm working on, we required both, so MySQL was not applicable. PostgreSQL, though, works fine, although I have to adjust to the differences from using SQLServer.

From what I've seen, MySQL is like MSSQLServer/SyBase, while PostgreSQL operates more like Oracle.

HTH!