select exam_id, duration, release_time from ( select exam_id, duration, release_time, 作答用时 - lag (作答用时, 1) over ( partition by exam_id order by 作答用时 asc ) 做差结果 from ( select ei.exam_id, duration, release_time, timestampdiff (second, start_time, submit_time) / 60 作答用时, rank() over ( partition by ei.e...