题解 | #分别满足两个活动的人#

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