题解 | #统计复旦用户8月练题情况#

#主要是分组和时间处理
select
    p.device_id,
    p.university,
    count(q.result) as total,
    sum(
        case
            when q.result = 'right' then 1 else 0
        end
    ) as p
from
    user_profile p
    left join question_practice_detail q on p.device_id = q.device_id
where
    p.university = '复旦大学'
    and (8 = MONTH (q.date) or q.date is null)
group by
    p.device_id