题解 | #统计复旦用户8月练题情况#

select
a.device_id as device_id
,b.university as university
,count(1) as question_cnt
,sum(if(a.result = 'right',1,0)) as right_question_cnt
from question_practice_detail a
left join user_profile b
on a.device_id = b.device_id
where b.university = '复旦大学'
and left(a.date,7) ='2021-08'
group by 1

union all

select
a.device_id as device_id
,a.university as university
,0 as question_cnt
,0 as right_question_cnt
from user_profile a
left join question_practice_detail b
on a.device_id = b.device_id
where b.device_id is null
and a.university = '复旦大学'