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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.