HAVING Clause
The HAVING clause can be used after the GROUP BY clause to provide filter criteria after the grouping has been completed. In terms of syntax the HAVING clause is identical to the WHERE clause, but while the WHERE clause occurs before the grouping, the HAVING clause occurs after the grouping.
Examples
-- count the number of entries in the "addresses" table that belong to each different city
-- filtering out cities with a count below 50
SELECT city, COUNT(*)
FROM addresses
GROUP BY city
HAVING COUNT(*) >= 50;
-- compute the average income per city per street_name
-- filtering out cities with an average income bigger than twice the median income
SELECT city, street_name, AVG(income)
FROM addresses
GROUP BY city, street_name
HAVING AVG(income) > 2 * MEDIAN(income);