关于oracle:Oracle分组取最大值

需要

该SQL是一个子SQL，须要查问出某个人所有过往履历中职务最高的

SELECT a."EMP_ID",a."CADRE_LEVEL"
  FROM (SELECT ROW_NUMBER() OVER(PARTITION BY EMP_ID ORDER BY CADRE_LEVEL DESC) rn,
               P_RESUME.*
          FROM P_RESUME) a where a.rn=1