Answer
Aggregate functions calculate one result from a set of input rows. • Common aggregates include COUNT, SUM, AVG, MIN, and MAX. • They can operate over the whole filtered result or once per GROUP BY group. • Most aggregates ignore null input values, while COUNT(*) counts rows.
💡 SQL Example
SELECT department_id, AVG(salary) FROM employees GROUP BY department_id;
Result
10 | 57500.00
⚡ Quick Revision
Aggregate functions summarize sets of rows.