select t2.author , substr(end_time,1,7) as month , round(sum(if(if_follow=1,1,if(if_follow=2,-1,0)))/count(start_time),3) , sum(sum(if(if_follow=1,1,if(if_follow=2,-1,0)))) over (partition by author order by substr(end_time,1,7)) as total_fan from tb_user_video_log join tb_video_info as t2 using (vi...