添加DELETE查询returns条重复记录 | SQL 服务器

Question

我需要你的帮助。

我有这个检测双工记录的查询：

SELECT
    name, email, COUNT(*)
FROM
    users
GROUP BY
    name, email
HAVING 
    COUNT(*) > 1

所以我需要删除结果，所以我尝试了这个：

Delete FROM
    users
GROUP BY
    name, email
HAVING 
    COUNT(*) > 1

但不起作用。可以告诉我一个帮助吗？谢谢

Answer 1

试试这个 query:

DELETE
FROM users
WHERE ID NOT IN
(SELECT MAX(ID)
FROM users
GROUP BY name, email)

Answer 2

由于你的问题中没有ID列（主键），假设没有ID列。所以下面的CTE会删除重复的记录。

;WITH CTE AS (
SELECT name
, email
, ROW_NUMBER() Over(Partition by name, email Order by(Select 1)) as Sno
FROM users
)
DELETE FROM CTE WHERE SNO>1

Answer 3

我假设您想要只是删除重复行而不是所有与重复行相关的行。

你可以在这里使用ROW_NUMBER。您还没有为 USERS table 提供整个架构，所以这里有一个例子

CREATE TABLE dbo.Users(
     Id INT IDENTITY(1,1)
    ,[Name] NVARCHAR(50)
    ,eMail NVARCHAR(50)
    ,DateCreated DATETIME
)

SELECT
     Id
    ,[Name]
    ,eMail
    ,DateCreated
    ,RN = ROW_NUMBER()OVER(PARTITION BY Name, eMail ORDER BY DateCreated ASC)  
FROM dbo.Users

您可以将此查询更改为通用 Table 表达式，然后您可以从中删除

;WITH cteDups
AS(
    SELECT
         Id
        ,[Name]
        ,eMail
        ,DateCreated
        ,RN = ROW_NUMBER()OVER(PARTITION BY Name, eMail ORDER BY DateCreated ASC)  
    FROM dbo.Users
)
DELETE FROM cteDups WHERE RN > 1

RN > 1只会删除重复的记录

添加DELETE查询returns条重复记录 | SQL 服务器

Add DELETE to query that returns duplicate records | SQL Server

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