如何删除表中的重复记录只保留其中一条
2016-09-20 16:08
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在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢?谢谢!
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)
比方说在A表中存在一个字段“name”,而且不同记录之间的“name”值有可能会相同,
现在就是需要查询出在该表中的各记录之间,“name”值存在重复的项;
Select Name,Count(*)
From A
Group By Name
Having Count(*)
>
1
如果还查性别也相同大则如下:
Select Name,sex,Count(*)
From A
Group By Name,sex
Having Count(*)
>
1
------------------------------------------------------------------------------------------------
declare
@max integer,@id
integer
declare cur_rows
cursor local for
select 主字段,count(*)
from 表名
group by 主字段
having count(*)
> ;
1
open cur_rows
fetch cur_rows
into @id,@max
while
@@fetch_status=0
begin
select
@max =
@max -1
set rowcount
@max
delete
from 表名 where 主字段
= @id
fetch cur_rows
into @id,@max
end
close cur_rows
set rowcount
0
方法二
有两个意义上的重复记录,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)
最后一个select即得到了Name,Address不重复的结果集(但多了一个autoID字段,实际写时可以写在select子句中省去此列)
select
* from tablename
where id in (
select id
from tablename
group
by id
having
count(id) >
1)
另外游标解决
declare @max integer,@id integer
declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having count(*) > 1
open cur_rows
fetch cur_rows into @id,@max
while fetch_status=0
begin
select @max = @max -1
set rowcount @max
delete from 表名 where 主字段 = @id
fetch cur_rows into @id,@max
end
close cur_rows
set rowcount 0
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)
比方说在A表中存在一个字段“name”,而且不同记录之间的“name”值有可能会相同,
现在就是需要查询出在该表中的各记录之间,“name”值存在重复的项;
Select Name,Count(*)
From A
Group By Name
Having Count(*)
>
1
如果还查性别也相同大则如下:
Select Name,sex,Count(*)
From A
Group By Name,sex
Having Count(*)
>
1
------------------------------------------------------------------------------------------------
declare
@max integer,@id
integer
declare cur_rows
cursor local for
select 主字段,count(*)
from 表名
group by 主字段
having count(*)
> ;
1
open cur_rows
fetch cur_rows
into @id,@max
while
@@fetch_status=0
begin
select
@max =
@max -1
set rowcount
@max
delete
from 表名 where 主字段
= @id
fetch cur_rows
into @id,@max
end
close cur_rows
set rowcount
0
方法二
有两个意义上的重复记录,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)
最后一个select即得到了Name,Address不重复的结果集(但多了一个autoID字段,实际写时可以写在select子句中省去此列)
select
* from tablename
where id in (
select id
from tablename
group
by id
having
count(id) >
1)
另外游标解决
declare @max integer,@id integer
declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having count(*) > 1
open cur_rows
fetch cur_rows into @id,@max
while fetch_status=0
begin
select @max = @max -1
set rowcount @max
delete from 表名 where 主字段 = @id
fetch cur_rows into @id,@max
end
close cur_rows
set rowcount 0
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