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mattm/left-join-sum.sql

Created November 1, 2017 18:09
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left-join-sum.sql
SELECT users.user_id, SUM(IF(post_id IS NULL, 0, 1)) AS post_count
FROM users
LEFT JOIN posts ON posts.user_id = users.user_id
GROUP BY 1
+---------+------------+
| user_id | post_count |
+---------+------------+
| 1 | 3 |
| 2 | 2 |
| 3 | 0 |
+---------+------------+
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