with cte as ( select course_id, time, sum(uv) over(partition by course_id order by time) as uv_sum from( select course_id, in_datetime as time, 1 as uv from attend_tb union all select course_id, out_datetime as time, -1 as uv from attend_tb )a ) select t1.course_id, t2.course_name, max(uv_sum) as ma...