本文介绍了单个查询中的 MySQL 多个计数的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我试图在单个查询中对两列进行计数，但结果为 medcount 和 uploadcount 吐出相同的值.有什么建议吗?
I am trying to COUNT two columns in a single query, but the results are spitting out the same values for medcount and uploadcount. Any suggestions?
SELECT * , COUNT($tbl_list.listname) AS listcount,
COUNT($tbl_uploads.id) AS uploadcount
FROM $tbl_members
LEFT JOIN $tbl_list ON $tbl_members.username = $tbl_list.username
LEFT JOIN $tbl_uploads ON $tbl_members.username = $tbl_uploads.username
GROUP BY $tbl_members.username
ORDER BY $tbl_members.lastname, $tbl_members.firstname;
推荐答案
使用:
SELECT tm.*,
x.listcount,
y.uploadcount
FROM $tbl_members tm
LEFT JOIN (SELECT tl.username,
COUNT(tl.listname) AS listcount
FROM $tbl_list tl
GROUP BY tl.username) x ON x.username = tm.username
LEFT JOIN (SELECT tu.username,
COUNT(tu.id) AS uploadcount
FROM $tbl_uploads tu
GROUP BY tu.username) y ON y.username = tm.username
GROUP BY tm.username
ORDER BY tm.lastname, tm.firstname
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