题解 | #牛客直播各科目出勤率#

# 简约算法
select t1.course_id,t2.course_name
,round(count(distinct(case when timestampdiff(minute,t3.in_datetime,t3.out_datetime)>=10 then t1.user_id else null end ))*100/count(distinct (case when t1.if_sign = 1 then t1.user_id else null end)),2)  as baoming
from behavior_tb as t1
left join attend_tb as t3
on t1.course_id = t3.course_id and t1.user_id = t3.user_id 
left join course_tb as t2 
on t1.course_id = t2.course_id 
group by t1.course_id,t2.course_name 
order by t1.course_id