当我尝试连接2个表并使用SUM或COUNT时，它们完全按预期工作。但是，当我连接3个表时，SUM和COUNT没有任何意义，因为JOIN语句为每个表创建额外的行以具有唯一的行，因此它们会超过计数并超过所需的值。
以下是查询：
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;
如果我运行两个单独的脚本，例如首次加入PO_club and PO_club_user以获取COUNT()，则可以正常运行。然后run PO_club JOIN PO_club_point_log让SUM()一切顺利。但是，我需要运行一个脚本，这样我就不需要在前端对它进行排序。是join 3 tables还是以COUNT()只在PO_club and PO_club_users SUM PO_club and PO_club_point_log上工作private void PasteFromExcel()
{
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？
谢谢！
答案 0 :(得分：0)
这是怎么回事？这将包括所有PO_clubs，即使他们没有任何用户，以防他们有积分。如果这不是您想要的，请将第一个LEFT JOIN更改为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