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
方法1
复制代码 代码如下:
delete yourtable
where [id] not in (
select max([id]) from yourtable
group by (name + value))
方法2
复制代码 代码如下:
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
查询及删除重复记录的sql语句
查询及删除重复记录的sql语句
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
复制代码 代码如下:
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
复制代码 代码如下:
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）
复制代码 代码如下:
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
复制代码 代码如下:
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
复制代码 代码如下:
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)
(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；
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
(三)
方法一
复制代码 代码如下:
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
＂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
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
复制代码 代码如下:
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
复制代码 代码如下:
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）
(四)
查询重复
复制代码 代码如下:
select * from tablename where id in (
select id from tablename
group by id
having count(id) > 1
)