select DISTINCT carnum from new_op_car_owner
delete from new_op_car_owner where carnum in(
select carnum from(
select max(carnum) as carnum,count(carnum) as count from new_op_car_owner group by carnum having count>1 order by count desc
) as tab
)
原文：http://www.cnblogs.com/shuixinwen/p/4065552.html