[英]SQL get unique month year combos
SELECT MONTH(sessionStart) AS Expr1, YEAR(sessionStart) AS Expr2
FROM tblStatSessions
WHERE (projectID = 187)
GROUP BY sessionStart
返回:
11 | 2010
11 | 2010
11 | 2010
12 | 2010
12 | 2010
但我需要它只返回一次實例,IE:
11 | 2010
12 | 2010
如果這是有道理的!
以下應該是你想要的:
SELECT MONTH(sessionStart) AS Expr1, YEAR(sessionStart) AS Expr2
FROM tblStatSessions
WHERE (projectID = 187)
GROUP BY MONTH(sessionStart), YEAR(sessionStart)
通常,您需要group by
所選的每個非聚合列進行group by
。 某些DBMS(例如Oracle)強制執行此操作,即不這樣做會導致錯誤而不是“奇怪”的查詢執行。
嘗試:
SELECT MONTH(sessionStart) AS Expr1, YEAR(sessionStart) AS Expr2
FROM tblStatSessions
WHERE (projectID = 187)
GROUP BY Expr1
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