NewbieNetwork: Using Aggregate Functions and Operators in PostgreSQLMay 11, 2001, 14:51 (1 Talkback[s])
(Other stories by Branden Williams)
"In Part 1 of this series, I will cover how to use the five most common and basic aggregate functions on PostgreSQL. Those functions are count(), min(), max(), avg(), and sum(). Look for more fun with aggregates and operators later in this series of articles."
"An aggregate function is a function such as count() or sum() that you can use to calculate totals. In writing expressions and in programming, you can use SQL aggregate functions to determine various statistics and values. Aggregate functions can greatly reduce the amount of coding that you need to do in order to get information from your database."