题解 | #第二快/慢用时之差大于试卷时长一半的试卷#

升序和降序各给数据算一次排序。 自连接，使用两种顺序为2的做题时间相减 ID降序。

	with a as((
	select e1.exam_id,e1.release_time,
	timestampdiff(minute,start_time,submit_time) diff,
	dense_rank()over(partition by exam_id order by  timestampdiff(second,start_time,submit_time)desc) diff1,
	dense_rank()over(partition by exam_id order by  timestampdiff(second,start_time,submit_time)asc) diff2,
	duration  from examination_info e1 
	left join exam_record e2
	on e1.exam_id=e2.exam_id ))
    select distinct a1.exam_id,a1.duration,a1.release_time from a a1
    left join a a2
    on a1.exam_id =a2.exam_id
    and a1.diff1=2 
    and a2.diff2=2
    where a1.diff-a2.diff >a1.duration/2
    order by exam_id desc