[英]SQL Combine Rows into Single Row
仍然在SQL上切入我的牙齒。 這是我目前的查詢(我會將其擴展為包含所有月份):
SELECT catid,
CASE WHEN MONTH(expdate) = '1' then SUM(expamount) END AS 'january',
CASE WHEN MONTH(expdate) = '2' then SUM(expamount) END AS 'february',
CASE WHEN MONTH(expdate) = '4' then SUM(expamount) END AS 'april'
FROM users LEFT JOIN (expcategories INNER JOIN expenses ON catid = catid_fk)
ON userid=userid_fk WHERE userid='1' GROUP BY catid, MONTH(expdate)
catid January February April
1 123.0000 NULL NULL
2 NULL 500.000 NULL
1 NULL NULL 505.0000
我希望特定catid
的結果返回單行,例如:
catid January February April
1 123.0000 NULL 505.0000
2 NULL 500.000 NULL
簡單回答:從GROUP BY
子句中刪除MONTH(expdate)
,並移動每個SUM
以包含其CASE
子句 - 如下所示:
SELECT catid,
SUM(CASE WHEN MONTH(expdate) = '1' then expamount END) AS 'january',
SUM(CASE WHEN MONTH(expdate) = '2' then expamount END) AS 'february',
SUM(CASE WHEN MONTH(expdate) = '4' then expamount END) AS 'april'
FROM users
LEFT JOIN (expcategories INNER JOIN expenses ON catid = catid_fk)
ON userid=userid_fk WHERE userid='1'
GROUP BY catid
(或者,考慮使用SQLServer的PIVOT
功能。)
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