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 situa