MySQL in a Nutshell, 2nd Edition

Aggregate Functions in Alphabetical Order

This section describes each aggregate function. Many of the examples use a subquery. For detailed information about subqueries, see the Subqueries” section later in this chapter.

A few general aspects of aggregate functions include:

• Aggregate functions return NULL when they encounter an error.

• Most uses for aggregate functions include a GROUP BY clause, which is specified in each description. If an aggregate function is used without a GROUP BY clause it operates on all rows.