選擇 COUNT 個非零單元格 mysql

Question

如何計算此查詢中非零的cc.audio值的COUNT ？

SELECT cc.audio FROM
(SELECT cid, SUM(mp='audio') audio, SUM(mp='text') texts, SUM(mp='video') video
FROM
  ( SELECT ccm.cid, cmp.cmid, cmp.mp
    FROM a as ccm
    INNER JOIN b as cmp
    ON ccm.mid = cmp.cmid) AS tmp
    GROUP BY cid) AS cc

樣本：

cid audio texts video   
----------------------
1    1      1     1
2    1      1     1 

Expected results: 2

Answer 1

你的問題表明：

SELECT COUNT(*)
FROM (
      SELECT cid, SUM(mp='audio') as audio, SUM(mp='text') as texts, SUM(mp='video') as video
      FROM a ccm INNER JOIN
           b cmp
           ON ccm.mid = cmp.cmid
      GROUP BY cid
    ) cc
WHERE audio > 0;

雖然我簡化了您的查詢，但基本相同。 還有其他方法可以寫這個，不涉及任何子查詢。