Oracle 重复数据查询以及删除

视频课：https://edu.csdn.net/course/play/7940

Create table test

(id number(2),

 names varchar2(20));

 insert into test values(1,'张三');
 insert into test values(2,'李四');
 insert into test values(3,'马七');

 select * from test;

 --查找重复数据
select * from test a where (a.id,a.names) in

 (select id,names from test group by id,names having count(*) > 1)

 --删除重复数据，只留rowid最小的那行；
 delete from test a where (a.id,a.names) in 

 (select id,names from test group by id,names having count(*) > 1)

  and rowid not in (select min(rowid) from test group by id,names having count(*)>1)
  --查找重复数据，不含rowid最小的行
  select * from test a where (a.id,a.names) in 
  (select id,names from test group by id,names having count(*) > 1) 
  and rowid not in (select min(rowid) from test group by id,names having count(*)>1) 
  

---1.以上是重复数据根据多列来判断

以下是重复数据根据单列来判断

1、首先，查找表中多余的重复记录，重复记录是根据单个字段（id）来判断

select * from test where id in(select id from test group by having count(id) >1)

2、删除表中多余的重复记录，重复记录是根据单个字段（id）来判断，只留有rowid最小的记录

delete from test where (id) in (select id from test group by id having count(id) >1) and rowid not in (select min(rowid) from test group by id having count(*)>1)