Question

我很遗憾在网上多次询问这个问题，但我不明白如何优化我的子查询：

 SELECT *
FROM rp_clientAffectationHistory as T1
WHERE rp_clientAffectationHistoryID in (SELECT MAX(rp_clientAffectationHistoryID)
        FROM rp_clientAffectationHistory as T2
GROUP BY `rp_clientID`)
AND `rp_userID` = 57

我有相同的“rp_clientID”的许多重复条目，我只想要有最新的rp_clientAffectationHistoryID的记录。

非常感谢

Answer 1

您需要的是：

SELECT *
  FROM Rp_Clientaffectationhistory AS T1
left join Rp_Clientaffectationhistory as T2 on (T1.Rp_Clientid = T2.Rp_Clientid) and T1.Rp_Clientaffectationhistoryid < T2.Rp_Clientaffectationhistoryid
where T2.Rp_Clientaffectationhistoryid is null
and T1.Rp_Userid = 57

有帮助吗？

Answer 2

我想你只想为每个rp_clientID -

获得一个条目

您错过的一件事是检查内部查询中的rp_clientID -

SELECT *
  FROM Rp_Clientaffectationhistory AS T1
 WHERE Rp_Clientaffectationhistoryid IN
       (SELECT MAX(Rp_Clientaffectationhistoryid)
          FROM Rp_Clientaffectationhistory AS T2
         WHERE T1.Rp_Clientid = T2.Rp_Clientid
         GROUP BY Rp_Clientid)
   AND Rp_Userid = 57

是你在寻找什么？

Answer 3

对于Sql server，请尝试：

SELECT * FROM(
    SELECT *, ROW_NUMBER() over (partition by rp_userID order by rp_clientAffectationHistoryID desc) Rnum 
    FROM rp_clientAffectationHistory
    WHERE rp_userID = 57
)x
WHERE Rnum=1

减少子查询加入

3 个答案: