如何删除没有唯一行id存在的重复行?

我的座位是

col1  col2 col3 col4 col5 col6 col7
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

我想留下以下重复删除后:

john  1    1    1    1    1    1
sally 2    2    2    2    2    2

我尝试了一些查询,但我认为他们取决于有一个行id,因为我没有得到想要的结果。例如:

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

当前回答

如果你没有引用,比如外键,你可以这样做。在测试概念证明和测试数据重复时,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。

其他回答

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
)

您需要根据字段对重复的记录进行分组,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)

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

在尝试了上面建议的解决方案后,它适用于小型中型表。 我可以为非常大的表提出这个解决方案。因为它在迭代中运行。

Drop all dependency views of the LargeSourceTable you can find the dependecies by using sql managment studio, right click on the table and click "View Dependencies" Rename the table: sp_rename 'LargeSourceTable', 'LargeSourceTable_Temp'; GO Create the LargeSourceTable again, but now, add a primary key with all the columns that define the duplications add WITH (IGNORE_DUP_KEY = ON) For example: 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 Create again the views that you dropped in the first place for the new created table Now, Run the following sql script, you will see the results in 1,000,000 rows per page, you can change the row number per page to see the results more often. Note, that I set the IDENTITY_INSERT on and off because one the columns contains auto incremental id, which I'm also copying

设置IDENTITY_INSERT LargeSourceTable ON 声明@PageNumber为INT, @RowspPage为INT 声明@TotalRows为INT 声明@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

请简单地在SELECT命令后添加关键字DISTINCT, 例如:

SELECT DISTICNT ColumnOne, ColumnTwo, ColumnThree
 FROM YourTable