Oracle 数据库中查询重复数据：

select * from employee group by emp_name having count (*)>1;

Oracle 查询可以删除的重复数据

select t1.* from employee t1 where (t1.emp_name) in (SELECT t2.emp_name from employee t2 group by emp_name having count (*)>1) and t1.emp_id not in (select min(t3.emp_id) from employee t3 group by emp_name having count (*)>1);

Oracle 删除重复数据

delete from employee t1 where (t1.emp_name) in (SELECT t2.emp_name from employee t2 group by emp_name having count (*)>1) and t1.emp_id not in (select min(t3.emp_id) from employee t3 group by emp_name having count (*)>1);