比如现在有一人员表 （表名：peosons）

若想将姓名、身份证号、住址这三个字段完全相同的记录查询出来 

select p1.*   

from persons p1,persons p2 

where p1.id<>p2.id   

and  p1.cardid = p2.cardid and p1.pname = p2.pname and p1.address = p2.address

 

可以实现上述效果．

 

几个删除重复记录的SQL语句

 

1.用rowid方法

 

2.用group by方法

 

3.用distinct方法

 

1。用rowid方法

 

据据oracle带的rowid属性，进行判断，是否存在重复,语句如下：

 

查数据:  www.2cto.com  

 

select * from table1 a where rowid !=(select max(rowid) 

from table1 b where a.name1=b.name1 and a.name2=b.name2......)

 

删数据：

 

delete  from table1 a where rowid !=(select max(rowid) 

from table1 b where a.name1=b.name1 and a.name2=b.name2......)

 

2.group by方法

 

查数据:

 

select count(num), max(name) from student --列出重复的记录数，并列出他的name属性 

group by num 

having count(num) >1 --按num分组后找出表中num列重复，即出现次数大于一次 

 

删数据：

 

delete from student 

group by num 

having count(num) >1

这样的话就把所有重复的都删除了。

 

3.用distinct方法 -对于小的表比较有用

 

create table table_new as   select distinct *   from table1 minux 

truncate table table1;

insert into table1 select * from table_new;

 

查询及删除重复记录的方法大全

 

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

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  www.2cto.com  

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,***,Count(*) From A Group By Name,*** 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  www.2cto.com  

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

)