SQL and Relational Theory, 3rd Edition

Preface to the Second Edition

The second edition differs from its predecessor in a number of ways. The overall objective remains the same, of course—using SQL relationally is still the emphasis—but the text has been revised throughout to reflect, among other things, experience gained from teaching live seminars based on the first edition.

One significant change is a deletion: The appendix on design theory has gone. There are two reasons for this change. First, design theory as such never really did have all that much to do with the book’s main message, anyway; second, the appendix was getting so extensive that it threatened to overwhelm the rest of the text. (It was already longer than any chapter or any other appendix in the book. In fact, I’ve since expanded that appendix into a separate book in its own right. That book—Database Design and Relational Theory: Normal Forms and All That Jazz—is due to be published soon by O’Reilly.² It can be seen as a companion, or perhaps a sequel, to the present book.)

On the positive side, a lot of new material has been added (including, importantly, a discussion of how to deal with missing information without using nulls); examples, exercises, and answers have been expanded and improved in various respects; and the treatment of SQL has been upgraded to cover recent changes to the SQL standard. A variety of corrections and numerous cosmetic improvements have also been made.³ (In particular, the Tutorial D examples—Tutorial D being the language ...