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sql重复记录怎么删除(SQL去除重复记录七种)

时间:2022-01-20 00:12:16类别:数据库

sql重复记录怎么删除

SQL去除重复记录七种

话不多说,请看代码:

  • if not object_id('Tempdb..#T') is null
     drop table #T
    Go
    Create table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2))
    Insert #T
    select 1,N'A',N'A1' union all
    select 2,N'A',N'A2' union all
    select 3,N'A',N'A3' union all
    select 4,N'B',N'B1' union all
    select 5,N'B',N'B2'
    Go 
    
  • --I、Name相同ID最小的记录(推荐用1,2,3),保留最小一条

    方法1:

    delete a from #T a where  exists(select 1 from #T where Name=a.Name and ID<a.ID)

    方法2:

  • delete a from #T a left join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null
    
  • 方法3:

    delete a from #T a where ID not in (select min(ID) from #T where Name=a.Name)

    方法4(注:ID为唯一时可用):

    delete a from #T a where ID not in(select min(ID)from #T group by Name)

    方法5:

    delete a from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)>0

    方法6:

    delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID)

    方法7:

  • delete a from #T a where ID>any(select ID from #T where Name=a.Name)
    select * from #T
    
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