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[英]Return sum of [column] and most recent value for [column] in the same query
[英]Return most recent row if column value matches from another column
假設我有一個名為UserID
的列和一個名為Active
Users的表,然后有一個稱為User History
。
我知道我可以獲取最近的用戶歷史記錄
select userid, field1, field2
from us_hi
where (userid,timestamp)
IN (select userid, max (timestamp)
from userhistory
group by userid)
order by userid
但是,如果我只想使用活動用戶表中的userid
查看活動用戶,該怎么辦?
子選擇將歷史記錄表中的所有用戶也存在於活動用戶表中,然后將子選擇與主查詢結合在一起,這應該為您提供所需的結果
SELECT USR.userid,field1, field2
FROM userhistory USR
INNER JOIN (SELECT UH.userid, max (UH.timestamp) timestamp
FROM userhistory UH
INNER JOIN ActiveUsers AU ON AU.UserId = UH.UserId
GROUP BY UH.userid) TMP ON TMP.userid = USR.userId AND USR.timestamp = UH.timestamp
ORDER BY USR.userid
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