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注:此处“重复”非完全重复,意为某字段数据重复 HZT表结构 ID int Title nvarchar(50) AddDate datetime 数据 一. 查找重复记录 1. 查找全部重复记录 Select * From 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1) 2. 过滤重复记录(只显示一条) Select * From HZT Where ID In (Select Max(ID) From HZT Group By Title) 注:此处显示ID最大一条记录 二. 删除重复记录
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sqlserver 删除重复记录处理(转)删除重复记录处理(转)
注:此处“重复”非完全重复,意为某字段数据重复
HZT表结构
ID int
Title nvarchar(50)
AddDate datetime
数据
一. 查找重复记录
1. 查找全部重复记录
Select * From 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)
2. 过滤重复记录(只显示一条)
Select * From HZT Where ID In (Select Max(ID) From HZT Group By Title)
注:此处显示ID最大一条记录
二. 删除重复记录
1. 删除全部重复记录(慎用)
Delete 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)
2. 保留一条(这个应该是大多数人所需要的)
Delete HZT Where ID Not In (Select Max(ID) From HZT Group By Title)
注:此处保留ID最大一条记录
其它相关:
删除重复记录有大小关系时,保留大或小其中一个记录
–> –> (Roy)生成測試數據
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
生成结果:
/*
ID Name Memo
———– —- —-
1 A A1
4 B B1
(2 行受影响)
*/
–II、Name相同ID保留最大的一条记录:
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 max(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 max(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 max(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 desc)
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