Question

我有一张桌子：

UserA UserB UserBB UserAA

例如：

我想要实现的是删除行（重复项），例如只留下行，例如：

1 2 2 1
1 3 3 1
2 4 4 2
2 5 5 2



2 1 1 2 -> deleted because there is already 1 2 2 1 
5 2 2 5 -> deleted because there is already 2 5 5 2

如何编写这样的查询？

感谢您的帮助

Answer 1

- 查找重复行

SELECT  MAX(ID) as ID, CustName, Pincode FROM #Customers
GROUP BY CustName, Pincode
HAVING COUNT(*) > 1

- 删除重复行

DELETE FROM #Customers
WHERE ID IN 
( SELECT    MAX(ID) FROM #Customers
GROUP BY CustName, Pincode
HAVING COUNT(*) > 1)

取自MSDN。： http://archive.msdn.microsoft.com/SQLExamples/Wiki/View.aspx?title=DuplicateRows

如果您无法从该代码中弄明白，请告诉我。

这可能会更接近您的需求。：

DELETE FROM TABLE
WHERE USERA IN ( SELECT MAX(USERA) FROM TABLE
GROUP BY USERA, USERB, USERBB, USERAA HAVING COUNT(*) > 1)

Answer 2

下面还介绍了UserA和UserB在两行之间相等但UserAA和UserBB切换相反的情况。你的问题有点不明确究竟是什么构成了重复。希望这至少可以指出你正确的方向。

我首先将它转换为SELECT语句，并确保它返回您认为应该删除的行，并且仅返回那些行。

DELETE T1
FROM
    My_Table T1
INNER JOIN My_Table T2 ON
    (
        T2.UserA = T1.UserA AND
        T2.UserB = T1.UserB AND
        T2.UserAA = T1.UserBB AND
        T2.UserBB = T1.UserAA AND
        T2.UserAA < T2.UserBB
    ) OR
    (
        T2.UserA = T1.UserB AND
        T2.UserB = T1.UserA AND
        T2.UserAA = T1.UserAA AND
        T2.UserBB = T1.UserBB AND
        T2.UserA < T2.UserB
    ) OR
    (
        T2.UserA = T1.UserB AND
        T2.UserB = T1.UserA AND
        T2.UserAA = T1.UserBB AND
        T2.UserBB = T1.UserAA AND
        T2.UserA < T2.UserB
    )

Answer 3

只需添加：

UserA＆lt;用户B

SQL从select中删除特定行

3 个答案: