注意：相差时长大于等于限定时长的一半

with t as 
(select t.exam_id,
        TIMESTAMPDIFF(MINUTE,start_time,submit_time) as time_gap,
        row_number()over(partition by exam_id order by TIMESTAMPDIFF(MINUTE,start_time,submit_time) desc) as rn1,
        row_number()over(partition by exam_id order by TIMESTAMPDIFF(MINUTE,start_time,submit_time)) as rn2
FROM examination_info t
join exam_record t1 on t.exam_id = t1.exam_id
where submit_time is not null
)
select t1.exam_id,duration,release_time
from examination_info t1
join 
(select exam_id,sum(if(rn1=2,time_gap,0))-sum(if(rn2=2,time_gap,0)) as total_time_gap
from t
group by exam_id) t2
on t1.exam_id = t2.exam_id
where total_time_gap>=duration/2
order by exam_id desc