题解 | 统计复旦用户8月练题情况

官方的太复杂了，看我的

select 
    u.device_id,u.university,
    count(q.question_id) as question_cnt,
    sum(case when q.result='right' then 1 else 0 end) as right_question_cnt
from user_profile as u 
    left join question_practice_detail as q 
    on u.device_id=q.device_id
    and month(q.date)=8
where u.university='复旦大学'
group by u.device_id, u.university;