#依据学校得出的平均发帖数

select avg(question_cnt) from user_profile group by university

#依据学校的出的平均回贴数

select avg(answer_cnt) from user_profile group by university

得出结果： select university,avg(question_cnt),avg(answer_cnt) from user_profile group by university having avg(question_cnt)<5 or avg(answer_cnt)<20 having对分组值进行过滤