SQL删除重复记录的N种方法

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 peoplewhere 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 peoplewhere 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 awhere (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 awhere (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 awhere (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

 

（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）

 

( 2）通过唯一rowid实现删除重复记录.在Oracle中，每一条记录都有一个rowid，rowid在整个数据库中是唯一的，rowid确定了每条记录是在Oracle中的哪一个数据文件、块、行上。在重复的记录中，可能所有列的内容都相同，但rowid不会相同，所以只要确定出重复记录中那些具有最大或最小rowid的就可以了，其余全部删除。

 

SQL>delete from employee e2 where rowid not in (        select max(e1.rowid) from employee e1 where

        e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and e1.salary=e2.salary);--这里用min(rowid)也可以。

 

SQL>delete from employee e2 where rowid <(        select max(e1.rowid) from employee e1 where         e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and

                  e1.salary=e2.salary);

（3）也是通过rowid，但效率更高。

 

SQL>delete from employee where rowid not in (        select max(t1.rowid) from employee t1 group by

         t1.emp_id,t1.emp_name,t1.salary);--这里用min(rowid)也可以。

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