赋予test_user查询scott用户emp表的权限
grant select on scott.emp to test_user;
基于scott用户的EMP表，使用test_user 创建EMP表
create table emp as select * from scott.emp;
再次插入相同的数据
insert into emp select * from emp;
查询当前数据
select * from emp order by empno asc;
可以看到每条记录出现了两次
1、删除表中多余的重复记录，重复记录是根据单个字段（EMPNO）来判断，只留有rowid最小的记录
delete from emp where empno in (select empno from emp group by empno having count(empno) > 1) and rowid not in (select min(rowid) from emp group by empno having count(empno)>1)
2、删除表中多余的重复记录，重复记录是根据多个字段（empno ,ename）来判断，只留有rowid最小的记录
delete from emp a where (a.empno ,a.ename) in (select empno,ename from emp group by empno,ename having count(*) > 1) and rowid not in (select min(rowid) from emp group by empno,ename having count(*)>1)
原文：http://www.cnblogs.com/xqzt/p/4482951.html