Sometimes the information you want can only be derived from data in a set of rows, instead of individual rows.
Aggregate functions produce results from sets of relational data that you have grouped (optionally) using a GROUP BY or ORDER BY clause. Aggregate functions process each set and produce one result for each set.
The following table lists a few examples of aggregate functions.
|
The function… |
Returns the… |
|
AVG |
arithmetic average of the values in a specified column. |
|
COUNT |
number of qualified rows. |
|
MAX |
maximum column value for the specified column. |
|
MIN |
minimum column value for the specified column. |
|
SUM |
arithmetic sum of a specified column. |