php - 为什么mysql查询返回零值?
问题描述
这是我的查询:
SELECT c.categoryName,
note1.*,
((SELECT SUM(noteAmount)
FROM notes
WHERE DATE_FORMAT(noteDate, '%d-%m-%Y') = DATE_FORMAT(note1.noteDate, '%d-%m-%Y') AND noteType = 'in')
-
(SELECT SUM(noteAmount)
FROM notes
WHERE DATE_FORMAT(noteDate, '%d-%m-%Y') = DATE_FORMAT(note1.noteDate, '%d-%m-%Y') AND noteType = 'out')) as trxCount
FROM notes AS note1
JOIN
(SELECT noteDate
FROM notes
GROUP BY noteDate
HAVING COUNT(noteDate) > 0)
AS note2
ON note1.noteDate = note2.noteDate
JOIN category c
ON c.categoryID = note1.categoryID
ORDER BY note1.noteDate ASC
看这个:
((SELECT SUM(noteAmount)
FROM notes
WHERE DATE_FORMAT(noteDate, '%d-%m-%Y') = DATE_FORMAT(note1.noteDate, '%d-%m-%Y') AND noteType = 'in')
-
(SELECT SUM(noteAmount)
FROM notes
WHERE DATE_FORMAT(noteDate, '%d-%m-%Y') = DATE_FORMAT(note1.noteDate, '%d-%m-%Y') AND noteType = 'out')) as trxCount
假设一天中只有一个收入数据(in)(没有支出数据)。例如 in = 15, and out = 0. 在查询中,我做了 [in - out] (15 - 0),但为什么我得到的是 0 而不是 15?
解决方案
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