题解 | 牛客直播各科目出勤率

with a as (select course_id, count(distinct user_id) attend
from attend_tb
where timestampdiff(minute,in_datetime,out_datetime) >=10
group by 1),
b as (select course_id, sum(if_sign) sign
from behavior_tb
group by 1)
select a.course_id, c.course_name, round(a.attend/b.sign*100,2) as "attend_rate(%)"
from a 
left join b on a.course_id=b.course_id
left join course_tb c on a.course_id=c.course_id
order by 1