What does HAVING do? How does HAVING differ from WHERE?

SQLJunior~1 min read

HAVING is used to filter results after grouping (GROUP BY). WHERE, on the other hand, is used to filter rows before grouping.

WHERE runs before GROUP BY, selecting individual rows;
HAVING runs after, selecting groups based on the results of aggregate functions.

sql

SELECT department, SUM(salary)
FROM employees
GROUP BY department
HAVING SUM(salary) > 100000;

Groups by department are formed first, then only the ones where the salary sum exceeds 100,000 remain.

If WHERE were used instead of HAVING, SQL wouldn't understand SUM(salary), because aggregates haven't been computed at that stage yet.

Interview ready

Premium

A concise answer to help you respond confidently on this topic during an interview.