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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