WITH t AS(
  SELECT 1 AS sno, 1 AS cno, 5 AS grade
    FROM dual
  UNION ALL
  SELECT 1, 2, 6
    FROM dual
  UNION ALL
  SELECT 1, 3, 10
    FROM dual
  UNION ALL
  SELECT 2, 3, 10
    FROM dual
  UNION ALL
  SELECT 2, 2, 10
    FROM dual
  UNION ALL
  SELECT 3, 1, 9
    FROM dual
  UNION ALL
  SELECT 3, 2, 9
    FROM dual)
  SELECT a.sno, Max(a.aa)
    FROM (SELECT sno,
                 wm_concat(cno || ',' || grade) over(partition BY sno order by cno, grade) AS aa
            FROM t) a
   GROUP BY a.sno;

运行一下就知道是啥意思了