请大家帮我看看哪里可以优化的~ with a as (select user_id,course_id,in_datetime dt,1 as uv from attend_tb union all select user_id,course_id,out_datetime dt,-1 as uv from attend_tb) select course_id,course_name,max(num) from (select b.course_id,b.num,c.course_name from (select course_id,sum(uv) over (partition...