當mysql查詢忽略限制時CASE的SUM（）

Question

我總共有4行。團隊ID 500有3勝1負。

下面的查詢預計會返回最多2個結果，記錄爲2-0或1-1，具體取決於是DESC還是ASC。

我一直得到3 &的結果1.我不確定在哪裏添加限制。

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

如果我理解正確，爲了實現您的目標，您必須在子查詢中應用LIMIT。 原因是LIMIT在收集結果集的過程中最後適用。

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 

這裏是SQLFiddle演示。