two-table-join.sql

SELECT
	users.user_id,
	COUNT(DISTINCT post_id) AS post_count,
	COUNT(DISTINCT page_id) AS page_count
FROM users
LEFT JOIN posts ON posts.user_id = users.user_id
LEFT JOIN pages ON pages.user_id = users.user_id
GROUP BY 1

+---------+------------+------------+
| user_id | post_count | page_count |
+---------+------------+------------+
|       1 |          3 |          0 |
|       2 |          2 |          2 |
|       3 |          0 |          5 |
+---------+------------+------------+