SQL · Chapter 22 of 42

SQL HAVING

HAVING filters GROUPED rows (i.e. after aggregation). WHERE filters raw rows BEFORE grouping.

Rule: WHERE for row-level filters, HAVING for group-level filters.

WHERE vs HAVING

`WHERE age > 18 GROUP BY country HAVING COUNT(*) > 10` first removes minors, then groups, then keeps countries with >10 adult users.

Example 1 (sql)

SELECT country, COUNT(*) AS users
FROM users
GROUP BY country
HAVING COUNT(*) > 10;

Output

only countries with >10 users

Filter groups by aggregate.

Example 2 (sql)

SELECT category, AVG(price) AS avg_p
FROM products
WHERE price > 0
GROUP BY category
HAVING AVG(price) > 500;

Output

categories with avg price over 500

WHERE + HAVING together.

💡 Note: If your HAVING clause has no aggregate, it should probably be a WHERE clause instead.