sql语句查询重复的数据

查找所有重复标题的记录：

SELECT *
FROM t_info a
WHERE ((SELECT
COUNT(*)
FROM t_info
WHERE Title = a.Title) > 1)
ORDER BY Title
DESC

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

1、查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断

select
* from people

where peopleId in (select peopleId from people group by
peopleId having count(peopleId) >
1)

2、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录

delete
from people

where peopleId in (select peopleId from people group by
peopleId having count(peopleId) > 1)

and rowid not in (select
min(rowid) from people group by peopleId having count(peopleId
)>1)

3、查找表中多余的重复记录（多个字段）

select * from vitae
a

where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by
peopleId,seq having count(*) >
1)

4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录

delete from vitae
a

where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by
peopleId,seq having count(*) > 1)

and rowid not in (select min(rowid)
from vitae group by peopleId,seq having
count(*)>1)

5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录

select *
from vitae a

where (a.peopleId,a.seq) in (select peopleId,seq from vitae
group by peopleId,seq having count(*) > 1)

and rowid not in (select
min(rowid) from vitae group by peopleId,seq having
count(*)>1)

补充：

有两个以上的重复记录，一是完全重复的记录，也即所有字段均重复的记录，二是部分关键字段重复的记录，比如Name字段重复，而其他字段不一定重复或都重复可以忽略。

1、对于第一种重复，比较容易解决，使用

select
distinct * from
tableName

就可以得到无重复记录的结果集。

如果该表需要删除重复的记录（重复记录保留1条），可以按以下方法删除

select
distinct * into #Tmp from tableName

drop table tableName

select *
into tableName from #Tmp

drop table
#Tmp

发生这种重复的原因是表设计不周产生的，增加唯一索引列即可解决。

2、这类重复问题通常要求保留重复记录中的第一条记录，操作方法如下

假设有重复的字段为Name,Address，要求得到这两个字段唯一的结果集

select
identity(int,1,1) as autoID, * into #Tmp from tableName

select
min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID

select *
from #Tmp where autoID in(select autoID from #tmp2)

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