题解 | 错误答案|个人笔记

having我这样写不对

select tag, difficulty, avg(score) clip_avg_score
from exam_record
     left join examination_info on examination_info.exam_id = exam_record.exam_id
where tag = 'SQL' and difficulty = 'hard'
group by tag, difficulty
having score != max(score) and score != min(score)

having为分组过滤条件，它对返回的结果集操作。

having字段不是有聚合函数就行，聚合函数是组筛选的条件

一般用 having max(column1) </>/= 某个值