Sams Teach Yourself SQL in 24 Hours, Fourth Edition

Chapter 15. Combining Multiple Queries into One

During this hour, you learn how to combine SQL queries into one by using the UNION, UNION ALL, INTERSECT, and EXCEPT operators. Once again, you must check your particular implementation for any variations in the use of these operators.

The highlights of this hour include:

• An overview of the operators used to combine queries

• When to use the commands to combine queries

• Using the GROUP BY clause with the compound operators

• Using the ORDER BY clause with the compound operators

• How to retrieve accurate data

By the Way

Some of the query operators covered in this hour are not currently supported by MySQL, as of the current release of version 5.0.45.

Single Queries Versus Compound Queries

The single query is one ...