在单个查询中使用多个MySQL计数

Question

我正在尝试在单个查询中计算两列，但是medcount和uploadcount的结果相同。 有什么建议吗？

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;

- Michael

Answer 1

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

- OMG Ponies