题解 | #统计复旦用户8月练题情况#

select
    a.device_id,
    a.university,
    count(q.question_id) question_cnt,
    sum(if(q.result = 'right',1,0)) right_question_cnt
from
    (
        select
            device_id,
            university
        from
            user_profile
        where
            university = '复旦大学'
    ) a
    left join question_practice_detail q on a.device_id = q.device_id
    and month (q.date) = 8
group by
    a.device_id