ORACLE 分组 排序出前面最大的N行

select  custid,carid,Cunote,INVNO,BUYPLAN 
from ( select custid,carid,Cunote,INVNO,BUYPLAN,
row_number() over(partition by custid,carid order by Feedbackid desc) rn
  from pvE3S.T_VCTM_CUSTOMER_FEEDBACK) t1 where rn=1

按Feedbackid 排序,rn是前N行