如何删除 SQL Server 中的重复行？

我喜欢 CTE 和 ROW_NUMBER，因为这两者的结合让我们可以看到哪些行被删除（或更新），因此只需将 DELETE FROM CTE... 更改为 SELECT * FROM CTE：

WITH CTE AS(
   SELECT [col1], [col2], [col3], [col4], [col5], [col6], [col7],
       RN = ROW_NUMBER()OVER(PARTITION BY col1 ORDER BY col1)
   FROM dbo.Table1
)
DELETE FROM CTE WHERE RN > 1

DEMO（结果不同；我认为这是由于您的拼写错误）

COL1    COL2    COL3    COL4    COL5    COL6    COL7
john    1        1       1       1       1       1
sally   2        2       2       2       2       2

由于 PARTITION BY col1，此示例通过单个列 col1 确定重复项。如果您想包含多个列，只需将它们添加到 PARTITION BY：

ROW_NUMBER()OVER(PARTITION BY Col1, Col2, ... ORDER BY OrderColumn)

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我更喜欢 CTE 从 sql server 表中删除重复的行

强烈建议关注这篇文章 ::http://codaffection.com/sql-server-article/delete-duplicate-rows-in-sql-server/

通过保持原始

WITH CTE AS
(
SELECT *,ROW_NUMBER() OVER (PARTITION BY col1,col2,col3 ORDER BY col1,col2,col3) AS RN
FROM MyTable
)

DELETE FROM CTE WHERE RN<>1

不保留原创

WITH CTE AS
(SELECT *,R=RANK() OVER (ORDER BY col1,col2,col3)
FROM MyTable)
 
DELETE CTE
WHERE R IN (SELECT R FROM CTE GROUP BY R HAVING COUNT(*)>1)

---

在不使用 CTE 和 ROW_NUMBER() 的情况下，您只需使用带有 MAX 功能的 group by 即可删除记录，这里是示例

DELETE
FROM MyDuplicateTable
WHERE ID NOT IN
(
SELECT MAX(ID)
FROM MyDuplicateTable
GROUP BY DuplicateColumn1, DuplicateColumn2, DuplicateColumn3)

---

如果你没有引用，比如外键，你可以这样做。在测试概念证明并且测试数据被重复时，我经常这样做。

SELECT DISTINCT [col1],[col2],[col3],[col4],[col5],[col6],[col7]

INTO [newTable]

FROM [oldTable]

进入对象资源管理器并删除旧表。

用旧表的名称重命名新表。

---

DELETE from search
where id not in (
   select min(id) from search
   group by url
   having count(*)=1

   union

   SELECT min(id) FROM search
   group by url
   having count(*) > 1
)

---

删除所有重复项，但最先删除（使用最小 ID）

应该在其他 SQL 服务器（如 Postgres）中同样工作：

DELETE FROM table
WHERE id NOT IN (
   select min(id) from table
   group by col1, col2, col3, col4, col5, col6, col7
)

---

mysql 中有两种解决方案：

A) 使用 DELETE JOIN 语句删除重复行

DELETE t1 FROM contacts t1
INNER JOIN contacts t2 
WHERE 
    t1.id < t2.id AND 
    t1.email = t2.email;

此查询引用了联系人表两次，因此，它使用表别名 t1 和 t2。

输出是：

1 个查询正常，4 行受影响（0.10 秒）

如果要删除重复行并保留 lowest id，可以使用以下语句：

DELETE c1 FROM contacts c1
INNER JOIN contacts c2 
WHERE
    c1.id > c2.id AND 
    c1.email = c2.email;

B) 使用中间表删除重复行

下面显示了使用中间表删除重复行的步骤：

1. 创建一个新表，其结构与要删除重复行的原始表相同。

2. 将原始表中的不同行插入到直接表中。

3. 将原始表中的不同行插入到直接表中。

步骤 1. 创建一个与原表结构相同的新表：

CREATE TABLE source_copy LIKE source;

步骤 2. 将原始表中的不同行插入到新表中：

INSERT INTO source_copy
SELECT * FROM source
GROUP BY col; -- column that has duplicate values

步骤 3. 删除原始表并将直接表重命名为原始表

DROP TABLE source;
ALTER TABLE source_copy RENAME TO source;

来源：http://www.mysqltutorial.org/mysql-delete-duplicate-rows/

---

请参阅下面的删除方式。

Declare @table table
(col1 varchar(10),col2 int,col3 int, col4 int, col5 int, col6 int, col7 int)
Insert into @table values 
('john',1,1,1,1,1,1),
('john',1,1,1,1,1,1),
('sally',2,2,2,2,2,2),
('sally',2,2,2,2,2,2)

创建了一个名为 @table 的示例表并使用给定数据加载它。

https://i.stack.imgur.com/DsYzT.png

Delete  aliasName from (
Select  *,
        ROW_NUMBER() over (Partition by col1,col2,col3,col4,col5,col6,col7 order by col1) as rowNumber
From    @table) aliasName 
Where   rowNumber > 1

Select * from @table

https://i.stack.imgur.com/qjapy.png

注意：如果您在 Partition by 部分中给出所有列，则 order by 没有太大意义。

我知道，这个问题是三年前提出的，我的回答是蒂姆发布的另一个版本，但发布只是以防万一它对任何人都有帮助。

---

在 sql server 中可以通过多种方式完成，最简单的方法是：将重复行表中的不同行插入到新的临时表中。然后从重复行表中删除所有数据，然后从没有重复的临时表中插入所有数据，如下所示。

select distinct * into #tmp From table
   delete from table
   insert into table
   select * from #tmp drop table #tmp

   select * from table

使用公用表表达式（CTE）删除重复行

With CTE_Duplicates as 
(select id,name , row_number() 
over(partition by id,name order by id,name ) rownumber  from table  ) 
delete from CTE_Duplicates where rownumber!=1

---

Microsoft 有一个关于如何删除重复项的非常简洁的指南。查看http://support.microsoft.com/kb/139444

简而言之，当您只有几行要删除时，这是删除重复项的最简单方法：

SET rowcount 1;
DELETE FROM t1 WHERE myprimarykey=1;

myprimarykey 是行的标识符。

我将 rowcount 设置为 1，因为我只有两行重复。如果我有 3 行重复，那么我会将 rowcount 设置为 2，以便它删除它看到的前两个，并且只在表 t1 中留下一个。

---

尝试使用：

SELECT linkorder
    ,Row_Number() OVER (
        PARTITION BY linkorder ORDER BY linkorder DESC
        ) AS RowNum
FROM u_links

https://i.stack.imgur.com/pUtkX.png

---

在尝试了上面建议的解决方案后，它适用于中小型表。我可以为非常大的表建议该解决方案。因为它在迭代中运行。

删除 LargeSourceTable 的所有依赖项视图，您可以使用 sql managment studio 找到依赖项，右键单击表并单击“查看依赖项” 重命名表：sp_rename 'LargeSourceTable', 'LargeSourceTable_Temp'; GO 再次创建 LargeSourceTable，但现在，添加一个主键，其中定义重复的所有列添加 WITH (IGNORE_DUP_KEY = ON) 例如： CREATE TABLE [dbo].[LargeSourceTable] ( ID int IDENTITY(1,1), [CreateDate] DATETIME CONSTRAINT [DF_LargeSourceTable_CreateDate] DEFAULT (getdate()) NOT NULL, [Column1] CHAR (36) NOT NULL, [Column2] NVARCHAR (100) NOT NULL, [Column3] CHAR (36) NOT NULL, PRIMARY KEY ( Column1, Column2) WITH (IGNORE_DUP_KEY = ON) ); GO 再次为新创建的表创建您首先删除的视图现在，运行以下 sql 脚本，您将看到每页 1,000,000 行的结果，您可以更改每页的行数以更频繁地查看结果.请注意，我将 IDENTITY_INSERT 设置为开和关，因为其中一列包含自动增量 id，我也在复制

SET IDENTITY_INSERT LargeSourceTable ON DECLARE @PageNumber AS INT, @RowspPage AS INT DECLARE @TotalRows AS INT declare @dt varchar(19) SET @PageNumber = 0 SET @RowspPage = 1000000 select @TotalRows = count (*) from LargeSourceTable_TEMP

While ((@PageNumber - 1) * @RowspPage < @TotalRows )
Begin
    begin transaction tran_inner
        ; with cte as
        (
            SELECT * FROM LargeSourceTable_TEMP ORDER BY ID
            OFFSET ((@PageNumber) * @RowspPage) ROWS
            FETCH NEXT @RowspPage ROWS ONLY
        )

        INSERT INTO LargeSourceTable 
        (
             ID                     
            ,[CreateDate]       
            ,[Column1]   
            ,[Column2] 
            ,[Column3]       
        )       
        select 
             ID                     
            ,[CreateDate]       
            ,[Column1]   
            ,[Column2] 
            ,[Column3]       
        from cte

    commit transaction tran_inner

    PRINT 'Page: ' + convert(varchar(10), @PageNumber)
    PRINT 'Transfered: ' + convert(varchar(20), @PageNumber * @RowspPage)
    PRINT 'Of: ' + convert(varchar(20), @TotalRows)

    SELECT @dt = convert(varchar(19), getdate(), 121)
    RAISERROR('Inserted on: %s', 0, 1, @dt) WITH NOWAIT
    SET @PageNumber = @PageNumber + 1
End

SET IDENTITY_INSERT LargeSourceTable OFF

---

要从 SQL Server 中的表中删除重复行，请按照下列步骤操作：

使用 GROUP BY 子句或 ROW_NUMBER() 函数查找重复行。使用 DELETE 语句删除重复的行。

设置样品表

DROP TABLE IF EXISTS contacts;

CREATE TABLE contacts(
    contact_id INT IDENTITY(1,1) PRIMARY KEY,
    first_name NVARCHAR(100) NOT NULL,
    last_name NVARCHAR(100) NOT NULL,
    email NVARCHAR(255) NOT NULL,
);

插入值

INSERT INTO contacts
    (first_name,last_name,email) 
VALUES
    ('Syed','Abbas','syed.abbas@example.com'),
    ('Catherine','Abel','catherine.abel@example.com'),
    ('Kim','Abercrombie','kim.abercrombie@example.com'),
    ('Kim','Abercrombie','kim.abercrombie@example.com'),
    ('Kim','Abercrombie','kim.abercrombie@example.com'),
    ('Hazem','Abolrous','hazem.abolrous@example.com'),
    ('Hazem','Abolrous','hazem.abolrous@example.com'),
    ('Humberto','Acevedo','humberto.acevedo@example.com'),
    ('Humberto','Acevedo','humberto.acevedo@example.com'),
    ('Pilar','Ackerman','pilar.ackerman@example.com');

https://i.stack.imgur.com/N9pU1.png

询问

    SELECT 
   contact_id, 
   first_name, 
   last_name, 
   email
FROM 
   contacts;

从表中删除重复的行

   WITH cte AS (
    SELECT 
        contact_id, 
        first_name, 
        last_name, 
        email, 
        ROW_NUMBER() OVER (
            PARTITION BY 
                first_name, 
                last_name, 
                email
            ORDER BY 
                first_name, 
                last_name, 
                email
        ) row_num
     FROM 
        contacts
)
DELETE FROM cte
WHERE row_num > 1;

现在应该删除记录

https://i.stack.imgur.com/B0T6K.png

---

with myCTE
as

(
select productName,ROW_NUMBER() over(PARTITION BY productName order by slno) as Duplicate from productDetails
)
Delete from myCTE where Duplicate>1

---

-- this query will keep only one instance of a duplicate record.
;WITH cte
     AS (SELECT ROW_NUMBER() OVER (PARTITION BY col1, col2, col3-- based on what? --can be multiple columns
                                       ORDER BY ( SELECT 0)) RN
         FROM   Mytable)



delete  FROM cte
WHERE  RN > 1

---

您需要根据字段对重复记录进行分组，然后保留其中一条记录并删除其余记录。例如：

DELETE prg.Person WHERE Id IN (
SELECT dublicateRow.Id FROM
(
select MIN(Id) MinId, NationalCode
 from  prg.Person group by NationalCode  having count(NationalCode ) > 1
 ) GroupSelect
 JOIN  prg.Person dublicateRow ON dublicateRow.NationalCode = GroupSelect.NationalCode 
 WHERE dublicateRow.Id <> GroupSelect.MinId)

---

从一个巨大的（几百万条记录）表中删除重复项可能需要很长时间。我建议您对选定行的临时表进行批量插入，而不是删除。

--REWRITING YOUR CODE(TAKE NOTE OF THE 3RD LINE) WITH CTE AS(SELECT NAME,ROW_NUMBER() 
OVER (PARTITION BY NAME ORDER BY NAME) ID FROM @TB) SELECT * INTO #unique_records FROM 
CTE WHERE ID =1;

---

这可能对您的情况有所帮助

DELETE t1 FROM table t1 INNER JOIN table t2 WHERE t1.id > t2.id AND t1.col1 = t2.col1 

---

With reference to https://support.microsoft.com/en-us/help/139444/how-to-remove-duplicate-rows-from-a-table-in-sql-server

删除重复的想法涉及

a) 保护那些不重复的行

b) 保留一起限定为重复的许多行之一。

一步步

1）首先确定满足重复定义的行并将它们插入到临时表中，例如 #tableAll 。

2）在临时表中选择非重复（单行）或不同的行，例如#tableUnique。

3) 从加入#tableAll 的源表中删除以删除重复项。

4) 将#tableUnique 中的所有行插入源表。

5) 删除#tableAll 和#tableUnique

---

如果您能够临时向表中添加一列，这是一个对我有用的解决方案：

ALTER TABLE dbo.DUPPEDTABLE ADD RowID INT NOT NULL IDENTITY(1,1)

然后使用 MIN 和 GROUP BY 的组合执行 DELETE

DELETE b
FROM dbo.DUPPEDTABLE b
WHERE b.RowID NOT IN (
                     SELECT MIN(RowID) AS RowID
                     FROM dbo.DUPPEDTABLE a WITH (NOLOCK)
                     GROUP BY a.ITEM_NUMBER,
                              a.CHARACTERISTIC,
                              a.INTVALUE,
                              a.FLOATVALUE,
                              a.STRINGVALUE
                 );

验证 DELETE 是否正确执行：

SELECT a.ITEM_NUMBER,
    a.CHARACTERISTIC,
    a.INTVALUE,
    a.FLOATVALUE,
    a.STRINGVALUE, COUNT(*)--MIN(RowID) AS RowID
FROM dbo.DUPPEDTABLE a WITH (NOLOCK)
GROUP BY a.ITEM_NUMBER,
    a.CHARACTERISTIC,
    a.INTVALUE,
    a.FLOATVALUE,
    a.STRINGVALUE
ORDER BY COUNT(*) DESC 

结果应该没有计数大于 1 的行。最后，删除 rowid 列：

ALTER TABLE dbo.DUPPEDTABLE DROP COLUMN RowID;

---

哦，哇，准备好所有这些答案让我觉得很愚蠢，它们就像专家对所有 CTE 和临时表等的回答。

我所做的只是使用 MAX 聚合 ID 列。

DELETE FROM table WHERE col1 IN (
    SELECT MAX(id) FROM table GROUP BY id HAVING ( COUNT(col1) > 1 )
)

注意：您可能需要多次运行它才能删除重复，因为这一次只会删除一组重复的行。

---

另一种在不丢失信息的情况下删除重复行的方法如下：

delete from dublicated_table t1 (nolock)
join (
    select t2.dublicated_field
    , min(len(t2.field_kept)) as min_field_kept
    from dublicated_table t2 (nolock)
    group by t2.dublicated_field having COUNT(*)>1
) t3 
on t1.dublicated_field=t3.dublicated_field 
    and len(t1.field_kept)=t3.min_field_kept

---

DECLARE @TB TABLE(NAME VARCHAR(100));
INSERT INTO @TB VALUES ('Red'),('Red'),('Green'),('Blue'),('White'),('White')
--**Delete by Rank**
;WITH CTE AS(SELECT NAME,DENSE_RANK() OVER (PARTITION BY NAME ORDER BY NEWID()) ID FROM @TB)
DELETE FROM CTE WHERE ID>1
SELECT NAME FROM @TB;
--**Delete by Row Number** 
;WITH CTE AS(SELECT NAME,ROW_NUMBER() OVER (PARTITION BY NAME ORDER BY NAME) ID FROM @TB)
DELETE FROM CTE WHERE ID>1;
SELECT NAME FROM @TB;

---

DELETE FROM TBL1  WHERE ID  IN
(SELECT ID FROM TBL1  a WHERE ID!=
(select MAX(ID) from TBL1  where DUPVAL=a.DUPVAL 
group by DUPVAL
having count(DUPVAL)>1))

---