Question

我有一个SQL表需要使用另一个表中的数据进行更新这似乎是一个非常简单的查询，但我无法更新我的表。

CustID      FirstCommunicationDate  SecondCommunicationDate
20144       2013/02/01      2013/02/16
20156       2013/02/10      2013/02/16
20755       2013/02/09      2013/02/16
20814       2013/04/14      2013/02/16
20903       2013/06/12      2013/02/16
21333       2013/06/21      2013/02/16


CustID      CommunicationNum    CommunicationDate
20144       1           2013/02/16
20144       1           2013/03/13
20144       2           2013/04/18
20903       1           2013/02/12
20903       1           2013/03/19
20903       2           2013/04/04
21333       1           2013/02/16
21333       1           2013/02/22
21333       2           2013/04/29

我的更新查询是：

UPDATE tblCommunication
SET FirstCommunicationDate = (SELECT MAX(CommunicationDate)
                FROM FieldData fd
                WHERE CustID = fd.CustID
                AND fd.CommunicationNum = 1)
WHERE CustID IN (SELECT CustID FROM FieldData)

我正在寻找的结果是：

CustID      FirstCommunicationDate  SecondCommunicationDate
20144       2013/03/13      2013/02/16
20903       2013/03/19      2013/02/16
21333       2013/02/22      2013/02/16

如何更新tblCommunication中的日期？

Answer 1

update a
set a.FirstCommunicationDate = b.MaxDate
from tblCommunication as a
inner join (select 
                CustID
                ,MAX(CommunicationDate) as MaxDate
            from FieldData
            where CommunicationNum = 1
            group by CustID) as b
    on a.CustID = b.CustID

Answer 2

试试这个

UPDATE tblCommunication
SET FirstCommunicationDate = (SELECT MAX(CommunicationDate)
                FROM FieldData fd
                WHERE t.CustID = fd.CustID
                AND fd.CommunicationNum = 1)
FROM tblCommunication t
WHERE t.CustID IN (SELECT CustID FROM FieldData)

SQL Update Table查询无效

2 个答案: