C. J. Date是關係數據庫技術領域中非常著名的獨立撰稿人、講師、學者和顧問。他撰寫瞭多部數據庫技術書籍，其中最齣名的著作是《數據庫係統導論》，這本書已經銷售瞭大約85萬冊，並被世界範圍內的幾百所大學作為教材使用。他因具有一流的將復雜技術進行清晰解讀的能力而享有盛譽。

Understanding SQL's underlying theory is the best way to guarantee that your SQL code is correct and your database schema is robust and maintainable. On the other hand, if you're not well versed in the theory, you can fall into several traps. In SQL and Relational Theory, author C.J. Date demonstrates how you can apply relational theory directly to your use of SQL. With numerous examples and clear explanations of the reasoning behind them, you'll learn how to deal with common SQL dilemmas, such as:

Should database access granted be through views instead of base tables?

Nulls in your database are causing you to get wrong answers. Why? What can you do about it?

Could you write an SQL query to find employees who have never been in the same department for more than six months at a time?

SQL supports "quantified comparisons," but they're better avoided. Why? How do you avoid them?

Constraints are crucially important, but most SQL products don't support them properly. What can you do to resolve this situation?

Database theory and practice have evolved since Edgar Codd originally defined the relational model back in 1969. Independent of any SQL products, SQL and Relational Theory draws on decades of research to present the most up-to-date treatment of the material available anywhere. Anyone with a modest to advanced background in SQL will benefit from the many insights in this book.