题解 | #牛客直播各科目出勤率#

select course_id,course_name,round(cnt1/cnt2*100,2) as attend_rate
from (
	select course_id,
				 course_name,
				 count(distinct if(timestampdiff(second,in_datetime,out_datetime)/60>=10,t2.user_id,null)) as cnt1,
				count(distinct t1.user_id) as cnt2
	from course_tb
	left join behavior_tb as t1 using(course_id)
	left join attend_tb as t2 using(course_id)
	where if_sign=1
	group by course_id,course_name
	) as t
order by course_id