题解 | #分别满足两个活动的人#

(select distinct uid, 'activity2' as activity
from exam_record left join examination_info on exam_record.exam_id=examination_info.exam_id
where difficulty='hard'
and timestampdiff(minute,start_time,submit_time)<0.5*duration
and score>80)
union all
(select distinct uid, 'activity1' as activity
from exam_record
where score >=85)
order by uid, activity

本来想创建两个临时表结果发现还不如union all连接的方便。并且为什么在union all 后使用order by activity 没有报错