Are there any topics you can already say you really know, or any you'd like to know about?
Do you already know all these things?
Fully understand all the joins,
the difference between ON and WHERE and HAVING (lots of people balls these up)
Indexing, using EXPLAIN to find out just how your SELECTs are working, then possibly having to force an index if it's being stupid
Transactions, and emulating them if you don't have the right table types available