MySQL by Paul DuBois is one of my favorites. Also, Joe Celko has a variety of advanced SQL books.
I also liked "Database Design for Mere Mortals" on how to properly design a database. It goes through the process and gives example of how to take paper-driven system and translate those into a real database. How to conduct interviews and actually get the information you need, then finally how to properly design and normalize your tables. I can't remember off the top of my head who the author is, but they're all on Amazon.