Simply put, Head First SQL is the bomb! A Slashdot review prompted me to order a copy from Amazon. This is one of few technical books on my shelf that will likely get put to use more than once! Perhaps it takes a creative female author to spark interest into an otherwise boring topic. Don't let the large fonts, pictures, and seemingly handwritten annotations fool you - Beighley leads you through some technical introductory SQL. The great thing is that her examples are about as simple as they could be given the topics she's teaching. It's not a reference, but good for anyone who isn't already a professional database admin/developer.
Head First SQL is uses MySQL in its examples, but is fairly vendor neutral. It does a great job explaining the basic rules of good database design. I have some level of appreciation for these concepts, but couldn't lay a finger on describing them in general. Her description of using atomic data in tables, particularly in discussing: one->one, one->many, and many->many relationships were informative and thought provoking. These concepts become VERY IMPORTANT as you try to update, edit, and query your data later. The book covered all the very basics up through things like: normal form, left inner joins, and using foreign keys.
Take the time to follow the examples in Head First SQL and you'll be a proficient SQL user in no time.