题解 | #分组过滤练习题#

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

# from 
# join 
# on 
# where 
# group by(开始使用select中的别名，后面的语句中都可以使用)
# avg,sum.... 
# having 
# select 
# distinct 
# order by
# limit