select uid,max(time_diff)+1 days_window, round(count(start_time)/(sum(time_diff)+1)*(max(time_diff)+1),2) avg_exam_cnt from( select uid,start_time, timestampdiff(day,DATE_FORMAT(pre_time,'%Y-%m-%d'),DATE_FORMAT(start_time,'%Y-%m-%d')) as time_diff from( select uid,start_time, lag(start_time,1) over(...