连接3个表时SQL使用计数和总和

Question

When I try to join 2 tables and use SUM or COUNT it all works perfectly and as expected. However when I join 3 tables SUM and COUNT makes no sense because the JOIN statements create extra rows for each table to have a unique row so they over count and over sum the required values.

Here is the query:

SELECT PO_club.clubid, PO_club.name, PO_club.pic, PO_club.points, count(PO_club_user.userid), SUM(PO_club_point_log.points)
FROM PO_club 
INNER JOIN PO_club_user ON PO_club.clubid = PO_club_user.clubid 
LEFT JOIN PO_club_point_log ON PO_club.clubid = PO_club_point_log.clubid 
WHERE PO_club.deleted = 0 
GROUP BY PO_club.clubid 
ORDER BY PO_club.points DESC;  

If I run two separate scripts like first join only PO_club and PO_club_user to get COUNT() it works. And then run PO_club JOIN PO_club_point_log to get SUM() its all good. However, I need to run it one script so that i would not need to sort it at the front end. Is there a way to join 3 tables and somehow COUNT() just work on PO_club and PO_club_users while SUM only on PO_club and PO_club_point_log ?

Thanks!

Answer 1

How's this? This will include all PO_clubs even if they don't have any users in case they have points. If that's not what you want, change the first LEFT JOIN to INNER JOIN .

SELECT PO_club.clubid, PO_club.name, PO_club.pic, PO_club.points, count(PO_club_user.userid), t.sum_points
FROM PO_club
LEFT JOIN PO_club_user ON PO_club.clubid = PO_club_user.clubid
LEFT JOIN
(SELECT PO_club_point_log.clubid, SUM(PO_club_point_log.points) AS sum_points
FROM PO_club_point_log INNER JOIN PO_club ON PO_club_point_log.clubid = PO_club.clubid
GROUP BY PO_club_point_log.clubid) AS t
ON PO_club.clubid = t.clubid
WHERE PO_club.deleted = 0
GROUP BY PO_club.clubid
ORDER BY PO_club.points DESC