这题和SQL 8思路一致 将in_time 和 out_time用UNION ALL并集,利用窗口函数计算每个时间段的瞬时uv select course_id, max(uv) as max_uv from ( select course_id, sum(inc) over (partition by course_id order by dt ,inc desc) as uv from ( select course_id,in_datetime dt, 1 inc from attend_tb union all select course_id,out_datetime dt, -...