题解 | #分组过滤练习题#

select t.university,t.avg_question_cnt,t.avg_answer_cnt
from(
    select university,avg(question_cnt) as avg_question_cnt,avg(answer_cnt) as avg_answer_cnt
    from user_profile
    group by university
)t
where t.avg_question_cnt<5 or t.avg_answer_cnt<20
#不命名为t之类的话，会编译错误
#也可以用having