I just finished the 800 pages that is Joe Celko’s SQL for Smarties: Advanced SQL Programming
This book is basically a massive set of examples of SQL solutions to a variety of problems. The text is divided into sections covering various areas like how NULLs can be handled and the use of temporary tables, with some repetition between the chapters. Some of the solutions are ingenious. This was a good introductions to some of the more advanced uses of SQL.
An excellent book.