题解 | #牛客直播各科目出勤率#

我回到了外面的标题，才注意到，是得出席10分钟及以上，这个条件题干里面没写

select a.course_id,
       a.course_name, 
       round((b.cnt/a.sign)*100,2) `attend_rate(%)`
from (select a.course_id , b.course_name , sum(if_sign) sign
      from behavior_tb a
      left join course_tb b
      on a.course_id = b.course_id
      group by a.course_id,b.course_name) a
left join (select course_id , count(distinct user_id) cnt
           from attend_tb
           where TIMESTAMPDIFF(minute,in_datetime,out_datetime) >= 10
           group by course_id) b
on a.course_id = b.course_id
order by a.course_id