In the world of large commercial databases, there are really only two choices: IBM's dB2 and Oracle. While MySQL and Postgres are increasingly try to break up this cosy duopoly, they are still small players. So as a professional DBA, or an aspiring one, dB2 is a good choice. Given this, IBM provides several levels of certification. Sanders here supplies the official study guide for the 701 and 706 exams.
Thumbing through this book, you see lots of SQL commands. But a lot of the SQL appears to be syntax specific to managing dB2. A dB2 programmer/user can largely deal with generic SQL. But for you, that's not enough. The value of this book is heavily in the specifics of dB2 and how to optimise its performance.
The questions and answers in each chapter are at least as important as the text. If you are at all serious, you MUST tackle these. Otherwise, you've just discarded half the value of the book. Of course, the actual questions in the exams will differ. But by being able to do the book's problems, it forces you to clarify your understanding.
My own SQL background is mostly with MySQL. So most of this book is new to me. I tried a couple of chapters and their problem sets. Not bad. The problems are not trivial. But the volume of material in each chapter is succinct enough to be doable in a few hours.