create table test1(
id number,
name varchar2(20)
);
insert into test1 values(1,'jack');
insert into test1 values(2,'jack');
insert into test1 values(3,'peter');
insert into test1 values(4,'red');
insert into test1 values(5,'green');
insert into test1 values(6,'green');
一 查询表中重复数据
1. 使用exists
select a.* from test1 a where exists (
select name from
( select name ,count(*)
from test1
group by name
having count(*)>1
) b
where a.name = b.name
);
2 join on
select a. * from test1 a
join (
select name ,count(*) from test1
group by name
having count(*)>1
) b
on a.name = b.name;
3 in
select a.name from test1 a
where a.name in
(
select name from test1
group by name
having count(*)>1
);
4 使用rowid 查询得到重复记录里，第一条插入记录后面的记录
select * from test1 a where rowid != (select min(rowid) from test1 b where b.name = a.name);
5 使用rowid查询得到重复记录里，最后一条记录之前插入的记录
select a.* from test1 a where rowid !=(select max(rowid) from test1 b where a.name=b.name);
6 使用rowid 查询得到 不重复的记录和重复记录里最后插入的一条记录
select a.* from test1 a where rowid =(select max(rowid) from test1 b where a.name=b.name);
7 使用rowid 查询得到不重复的记录和重复记录里最先插入的记录
select * from test1 a where rowid = (select min(rowid) from test1 b where b.name = a.name);
删除 所有重复不保留任何一条
delete from test1 a where exists ( select name from (select name ,count(*) from test1 group by name having count(*)>1) b where a.name = b.name);
delete from test1 a where a.name in (select name from test1 group by name having count(*)>1);
删除重复记录里，第一条重复记录后面插入的记录
delete from test1 a where rowid !=(select min(rowid) from test1 b where b.name = a.name);
删除先前插入的重复记录，保留最后插入的重复记录
delete from test1 a where rowid !=(select max(rowid) from test1 b where a.name=b.name);