HAVING

The HAVING clause filters the results of a GROUP BY operation based on a condition. While the WHERE clause filters rows before they are grouped, the HAVING clause filters groups after they are formed.

Columns referenced in the HAVING clause must either be part of the GROUP BY clause or be used within an aggregate function.

Filter groups based on a condition on the grouping column:

SELECT state_abbr, SUM(population)
FROM cities
GROUP BY state_abbr
HAVING state_abbr = 'OH';

Filter groups based on an aggregate value:

SELECT state_abbr, SUM(population)
FROM cities
GROUP BY state_abbr
HAVING SUM(population) > 1000000;

Any aggregate function can be used in the HAVING clause, not just ones that appear in the SELECT clause. For example, we can limit our per-state population totals just to states that we have more than 10 cities for:

SELECT state_abbr, SUM(population)
FROM cities
GROUP BY state_abbr
HAVING COUNT(*) > 10;