Database in Depth

Preface

After many years working in the database community in various capacities, I've come to realize there's a real need for a book for practitioners (not novices) that explains the basic principles of relational theory in a way not tainted by the quirks and peculiarities of existing products, commercial practice, or the SQL standard. I wrote this book to fill that need. My intended audience is thus experienced database practitioners or other database professionals who are honest enough to admit they don't understand the theory underlying their own field as well as they might, or should. That theory is, of course, the relational model—and while it's true that the fundamental ideas of that theory are all quite simple, it's also true that they're widely misrepresented, or underappreciated, or both. Often, in fact, they don't seem to be understood at all. For example, here are a few relational questions. How many of them can you answer?

1. What exactly is first normal form?

2. What's the connection between relations and predicates?

3. What's semantic optimization?

4. What's a join dependency?

5. Why is semidifference important?

6. Why doesn't deferred integrity checking make sense?

7. What's a relation variable?

8. What's nonloss decomposition?

9. Can a relation have an attribute whose values are relations?

10. What's the difference between SQL and the relational model?

11. Why is The Information Principle important?

12. How does XML fit with the relational model?

This book provides answers to these and many related questions. Overall, ...