Sometimes the information you want can be derived only 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.
Examples of aggregate functions:
| Function | Returned Value |
|---|---|
| AVG | Arithmetic average of values in specified column. |
| COUNT | Number of qualified rows. |
| MAX | Maximum value in specified column. |
| MIN | Minimum value in specified column. |
| SUM | Arithmetic sum values in specified column. |