题解 | 统计复旦用户8月练题情况

1.将两个表用left join基于up.device_id = qpd.device_id左连接，提取复旦大学用户；

2.按照device_id分组；

3.按照条件用sum函数统计练题总数和正确数，重命名。

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