题解 | #分组过滤练习题#
分组过滤练习题
https://www.nowcoder.com/practice/ddbcedcd9600403296038ee44a172f2d
select university, round(avg(question_cnt),3) as avg_question_cnt, round(avg(answer_cnt),3) as avg_answer_cnt from user_profile group by university having avg(question_cnt)<5 or avg(answer_cnt)<20
where子句在聚合前先筛选记录,也就是说作用在group by 子句和having子句前,而 having子句在聚合后对组记录进行筛选