题解 | #分别满足两个活动的人#

select distinct uid,'activity1' as activity
from  exam_record
where year(start_time)=2021
group by uid
# having min(score)>=85
having avg(if(score>=85,1,0))=1
union all
select distinct uid,'activity2' as activity
from examination_info as ei left join exam_record as er
using(exam_id)
where timestampdiff(minute,start_time,submit_time)<0.5*duration 题目有表述不清的问题 一开始这个符号用的<=一直不对
  and difficulty='hard'
  and score>80
  and year(start_time)=2021 还有这个地方为什么用开始时间而不是提交时间呢 这个也不够明晰
group by uid
order by uid