mysql删除多列重复记录

delete lring_class_score as a from lring_class_score as a,
(
select *,min(lcsid) from lring_class_score group by jobnumber,classid,courseid having count(1) > 1
) as b
 where a.jobnumber = b.jobnumber and a.classid=b.classid and a.courseid=b.courseid and a.lcsid >

b.lcsid;