题解 | 牛客直播各科目出勤率

select t1.course_id,course_name,round((count1/count2)*100,2) attend_rate
from
(select at.course_id course_id,course_name,count(distinct user_id) count1
from attend_tb at
join course_tb ct
on at.course_id = ct.course_id
where timestampdiff(minute,in_datetime,out_datetime) >= 10
group by at.course_id,course_name) as t1
join 
(select course_id,count(1) count2
from behavior_tb bt 
where if_sign = 1
group by course_id) as t2
on t1.course_id = t2.course_id
order by t1.course_id