题解 | #统计复旦用户8月练题情况#

select 
    t1.device_id,
    t1.university,
    sum(
        case when t2.id is not null 
        then 1
        else 0
        end 
    ) question_cnt,
    sum(case
        when t2.result ='right'
        then 1
        else 0 end ) right_question_cnt

from 
    user_profile t1
left join 
    question_practice_detail t2
on 
    t1.device_id = t2.device_id
where
    t1.university = '复旦大学'
    and (month(t2.date) = 8 or month(t2.date) is null)
group by
    t1.device_id,t1.university