MySQL单次查询中的多个计数 [英] MySQL Multiple Counts in Single Query

问题描述

我想在一个查询中COUNT两列，但结果是吐出相同的medcount和uploadcount的值。任何建议？

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

这篇关于MySQL单次查询中的多个计数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！