[英]MySQL if statement returning incorrect results with aggregate function
我有一個查詢
SELECT
itemId, userId, source
FROM table
WHERE itemId = 1 AND userId = 1 and source = 1;
它返回20行,其中itemId為1,userId為1,源為1(對於實例)。 在我的數據庫中,此itemId和userID包含更多行,它們具有不同的來源。 我想獲得一些統計數據。
為什么此查詢為什么唯一行和總數行都返回0?
SELECT ID,
IF(source = 1, COUNT(DISTINCT userId), 0) as 'unique',
IF(source = 1, COUNT(userId), 0) as 'total'
FROM table
WHERE itemId = 1 AND userId = 1;
GROUP BY itemId;
提前致謝。
使用條件COUNT()
SELECT itemId
, COUNT( DISTINCT CASE WHEN source = 1
THEN userId
END) as 'unique'
, COUNT( CASE WHEN source = 1
THEN userId
END) as 'total'
FROM yourTable
WHERE itemId = 1 AND userId = 1
GROUP BY itemId
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