一、题目 有学生每科科目成绩,找出所有科目成绩都大于对应学科的平均成绩的学生 +------+------+--------+ | sid | cid | score | +------+------+--------+ | 1 | 1 | 90 | | 1 | 2 | 50 | | 1 | 3 | 72 | | 2 | 1 | 40 | | 2 | 2 | 50 | | 2 | 3 | 22 | | 3 | 1 | 30 | | 3 | 2 | 50 | | 3 | 3