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 delete yourtable where [id] not in ( select max([id]) from yourtable group
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
delete yourtable
where [id] not in (
select max([id]) from yourtable
group by (name + value))
方法2
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
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)
(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
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
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)
(四)
查询重复
select * from tablename where id in (
select id from tablename
group by id
having count(id) > 1
)
学习sql有一段时间了，发现在我建了一个用来测试的表(没有建索引)中出现了许多的重复记录。后来总结了一些删除重复记录的方法，在oracle中，可以通过唯一rowid实现删除重复记录;还可以建临时表来实现...这个只提到其中的几种简单实用的方法，希望可以和大家分享(以表employee为例)。
sql> desc employee
name null? type
----------------------------------------- -------- ------------------
emp_id number(10)
emp_name varchar2(20)
salary number(10,2)
可以通过下面的语句查询重复的记录：
sql> select * from employee;
emp_id emp_name salary
---------- ---------------------------------------- ----------
1 sunshine 10000
1 sunshine 10000
2 semon 20000
2 semon 20000
3 xyz 30000
2 semon 20000
sql> select distinct * from employee;
emp_id emp_name salary
---------- ---------------------------------------- ----------
1 sunshine 10000
2 semon 20000
3 xyz 30000
sql> select * from employee group by emp_id,emp_name,salary having count (*)>1
emp_id emp_name salary
---------- ---------------------------------------- ----------
1 sunshine 10000
2 semon 20000
sql> select * from employee e1
where rowid in (select max(rowid) from employe e2
where e1.emp_id=e2.emp_id and
e1.emp_name=e2.emp_name and e1.salary=e2.salary);
emp_id emp_name salary
---------- ---------------------------------------- ----------
1 sunshine 10000
3 xyz 30000
2 semon 20000
2. 删除的几种方法：
(1)通过建立临时表来实现
sql>create table temp_emp as (select distinct * from employee)
sql> truncate table employee; (清空employee表的数据)
sql> insert into employee select * from temp_emp; (再将临时表里的内容插回来)
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