题解 | #试卷发布当天作答人数和平均分#
作答试卷得分大于过80的人的用户等级分布
http://www.nowcoder.com/practice/5bc77e3a3c374ad6a92798f0ead4c744
select level, count(distinct uid) as level_cnt from exam_record join examination_info using (exam_id) join user_info using (uid) where tag = 'SQL' and score > 80 group by level order by level_cnt desc, level desc
将三个表连起来，确认两个筛选条件，一个分组条件和两个排序条件即可
