Question

我总共有4行。球队ID 500有3胜1负。

下面的查询预计会返回最多2个结果，记录为2-0或1-1，具体取决于它是DESC还是ASC。

我一直得到3＆amp;的结果1.我不确定在哪里添加限制。

SELECT SUM(CASE WHEN `winner` = 500 THEN 1 ELSE 0 END) AS wins,
       SUM(CASE WHEN `loser` = 500 THEN 1 ELSE 0 END) AS losses
FROM  `schedule`
WHERE  500 IN (`winner`, `loser`)
ORDER BY `date` DESC
LIMIT 2;

Answer 1

如果我理解正确，为了实现目标，您必须在子查询中应用LIMIT。原因是LIMIT在收集结果集的过程中最后应用。

SELECT SUM(CASE WHEN `winner` = 500 THEN 1 ELSE 0 END) AS wins,
       SUM(CASE WHEN `loser`  = 500 THEN 1 ELSE 0 END) AS losses
FROM  
(
  SELECT * 
    FROM schedule 
   WHERE  500 IN (`winner`, `loser`)
   ORDER BY `date` DESC
   LIMIT 2
) q

这是 SQLFiddle 演示。

CASE的SUM（）WHEN mysql查询忽略限制

1 个答案: