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sql数据库中删除重复记录sql语句大全
来源: 互联网 发布时间：2014-08-29
本文导语: sql数据库如何删除重复记录呢？这个问题我们并不陌生，在之前脚本学堂整理的文章中，有不少这样的例子。 最简单的就是一条sql语句删除表中重复记录，多用于处理紧急的、或简单易解决的数据重复问题。 在sql数据库中，...
sql数据库如何删除重复记录呢？这个问题我们并不陌生，在之前脚本学堂整理的文章中，有不少这样的例子。
最简单的就是一条sql语句删除表中重复记录，多用于处理紧急的、或简单易解决的数据重复问题。在sql数据库中，常用distinct筛选重复记录，这个主要用于前期的重复记录判断与比对，掌握了有哪些重复数据之后，接下来就是借助： sql server 查询重复记录的多种方法完成重复记录的删除了。
当然，有时会遇到一些个性化的数据筛选与删除需求，比如sql server 重复记录的取最新一笔以及sql server删除重复记录且只余一条，都可以轻松实现。
在sql数据库中，提到重复记录的问题，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：
代码示例:
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），可以这样删除：
代码示例:
select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp
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
代码示例:
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)
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）
3、部分关键字段重复，且记录中有ID.
第一种方法可一次删除所有重复的..(只保留重复中ID最小的记录)。
代码示例:
delete from table where id not in ( select min(id) from table group by name)
第二种方法每次只删除重复中ID最大的一条记录。
代码示例:
delete from table where id in ( select max(id) from table group by name having count(*)>1)
4、SQL程序删除
代码示例:
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
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
自己还得出的办法：
select * from user1 where [id] not in (select top 1 [id] from user1 a where name=user1.name)
--删就这样写
delete from user1 where [id] not in (select top 1 [id] from user1 a where name=user1.name)
或 delete from user where id not in ( select max(id) from user where name=user.name)
delete [user] where id not in (select max(id) from [user] group by name having count(*) > 1)
max 或 min看具体情况而论。
--删就这样写
delete from user1 where [id] not in (select top 1 [id] from user1 a where name=user1.name)
或 delete from user where id not in ( select max(id) from user where name=user.name)
delete [user] where id not in (select max(id) from [user] group by name having count(*) > 1)
max 或 min看具体情况而论。
其他方法：
代码示例:
----A:保留id最大的行,删除其它行
-- 方法1
delete [user] from [user] t
inner join(select name,max(id) as id from [user] group by name) a
on t.name = a.name and t.id a.id
--方法2
delete [user] from [user] t
where exists(select * from [user] where name = t.name and id > t.id)
----B:保留id最小的行,删除其它行
--方法1
delete [user] from [user] t
inner join(select name,min(id) as id from [user] group by name) a
on t.name = a.name and t.id a.id
--方法2
delete [user] from [user] t
where exists(select * from [user] where name = t.name and id 1)) as b
on t.id = b.id
-- 方法1
delete [user] from [user] t
inner join(select name,max(id) as id from [user] group by name) a
on t.name = a.name and t.id a.id
--方法2
delete [user] from [user] t
where exists(select * from [user] where name = t.name and id > t.id)
----B:保留id最小的行,删除其它行
--方法1
delete [user] from [user] t
inner join(select name,min(id) as id from [user] group by name) a
on t.name = a.name and t.id a.id
--方法2
delete [user] from [user] t
where exists(select * from [user] where name = t.name and id 1)) as b
on t.id = b.id
附，用SQL删除重复记录的N种方法
标签： 删除重复记录 it 分类： 学习笔记
例如：
id name value
1 a pp
2 a pp
3 b iii
4 b pp
5 b pp
6 c pp
7 c pp
8 c iii
id是主键
要求得到这样的结果
id name value
1 a pp
3 b iii
4 b pp
6 c pp
8 c iii
1 a pp
2 a pp
3 b iii
4 b pp
5 b pp
6 c pp
7 c pp
8 c iii
id是主键
要求得到这样的结果
id name value
1 a pp
3 b iii
4 b pp
6 c pp
8 c iii
方法1
代码示例:
delete YourTable
where [id] not in (
select max([id]) from YourTable
group by (name + value))
where [id] not in (
select max([id]) from YourTable
group by (name + value))
方法2
代码示例:
delete a
from 表 a left join(
select id=min(id) from 表 group by name,value
)b on a.id=b.id
where b.id is null
from 表 a left join(
select id=min(id) from 表 group by name,value
)b on a.id=b.id
where b.id is null
查询及删除重复记录的sql语句大全
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
代码示例:
select * from people
where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
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
代码示例:
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)
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）
代码示例:
select * from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
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
代码示例:
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)
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
代码示例:
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)
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)
(二)
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；
代码示例:
Select Name,Count(*) From A Group By Name Having Count(*) > 1
如果还查性别也相同大则如下:
代码示例:
Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1
(三)
方法一
代码示例:
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
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
＂重复记录＂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
代码示例:
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
代码示例:
select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp
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
代码示例:
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)
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）
四)查询重复
代码示例:
select * from tablename where id in (
select id from tablename
group by id
having count(id) > 1
)
select id from tablename
group by id
having count(id) > 1
)
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