select distinct rk.exam_id,duration,release_time from (     select exam_id,     nth_value(timestampdiff(second,start_time,submit_time),2)over(partition by exam_id order by timestampdiff(second,start_time,submit_time))&nb...

select distinct uid,'activity1' activity from examination_info left join exam_record using(exam_id) group by uid having min(score)>=85 union all select distinct uid,'activity2' activity from examination_info left join&nbsp...

select exam_id, count(distinct uid) uv, round(avg(score),1) avg_score from user_info join exam_record using(uid) join examination_info using(exam_id) where tag='SQL' and day(start_time)=day(release_time) and month(start_time)=month(start_time) and&nb...