Mysql use query result in new query - mysql

Question

So I have two tables one called points_log and one called leaderboard.
mysql> describe points_log;
+---------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------+---------+------+-----+---------+-------+
| user_id | int(11) | NO | | NULL | |
| points | int(11) | YES | | 0 | |
| date | date | NO | | NULL | |
+---------+---------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> describe leaderboard;
+-----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+--------------+------+-----+---------+-------+
| bucket | varchar(255) | YES | | NULL | |
| user_id | int(11) | YES | | NULL | |
| school_id | int(11) | YES | | NULL | |
+-----------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
I have the following query:
SELECT leaderboard.user_id FROM leaderboard where
leaderboard.bucket=(SELECT bucket FROM leaderboard WHERE leaderboard.user_id=$user_id) AND
leaderboard.school_id = (SELECT school_id FROM leaderboard WHERE leaderboard.user_id=$user_id)
This will return one or more rows with user_id's that are in the bucket with $user_id passed in. What I want to do is take all of those user_id's and find run the following query
SELECT sum(points) FROM points_log WHERE user_id=$user_id AND
date >= (SELECT subdate(curdate(), INTERVAL (weekday(now())) DAY))
The issue is this second query if not guaranteed to return something, so in the case that it doesn't return anything I want sum(points) to be 0. I also need to return the user_id,bucket, and sum(points) for each row.
Right now what I have is
SELECT leaderboard.user_id,sum(points_log.points) AS points, leaderboard.bucket
FROM points_log LEFT JOIN leaderboard ON points_log.user_id = leaderboard.user_id
WHERE points_log.DATE >= (SELECT subdate(curdate(), INTERVAL (weekday(now())) DAY))
AND leaderboard.bucket=(SELECT bucket FROM leaderboard WHERE leaderboard.user_id=$user_id)
AND leaderboard.school_id = (SELECT school_id FROM leaderboard WHERE leaderboard.user_id=$user_id)
GROUP BY USER_ID ORDER BY SUM(points) DESC
The issue with this is that it only works when there is a value in points_log for that user. I'm unsure how to make it default to 0 if there is no value.
Any help is greatly appreciated!

Answer 1

SELECT leaderboard.user_id, COALESCE( sum(points_log.points), 0 )AS points, leaderboard.bucket
FROM points_log RIGTH OUTER JOIN leaderboard ON points_log.user_id = leaderboard.user_id
WHERE points_log.DATE >= (SELECT subdate(curdate(), INTERVAL (weekday(now())) DAY))
AND leaderboard.bucket=(SELECT bucket FROM leaderboard WHERE leaderboard.user_id=$user_id)
AND leaderboard.school_id = (SELECT school_id FROM leaderboard WHERE leaderboard.user_id=$user_id)
GROUP BY USER_ID ORDER BY SUM(points) DESC
Try this... note the Outer Join and the COALESCE function.