题解 | #分组过滤练习题#

select
    e.university,
    round (avg(e.question_cnt) , 3) as avg_question_cnt,
    round (avg(e.answer_cnt) , 3) as avg_answer_cnt
from
    user_profile e
group by
    e.university
having avg(e.question_cnt) < 5  or avg(e.answer_cnt) <20

where用于筛选原有字段，having用于筛选新建字段