Where can I find database tuning exercises for learning? As a developer, often DBAs take responsibility for resolving performance issues at the database level so we don't get that much experience diagnosing, tuning, refactoring queries etc. 

I'm looking for a database with a bunch of tables, data, queries, triggers, SPs and so on, in which there are deliberate performance problems, and hopefully a series of exercises in which you attempt to identify and resolve the problems. Ideally this will be on MS SQL server.

Anyone know of this kind of thing?
Paul Randal provides some sample DBs that are actually corrupt: http://www.sqlskills.com/BLOGS/PAUL/post/Conference-corruption-demo-scripts-and-example-corrupt-databases.aspx

Good exercise to go through working with DBCC commands and such on SQL Server.