题解 | #分别满足两个活动的人#

(
    select
        uid,
        'activity1' as activity
    from
        exam_record er
    where
        year (start_time) = '2021'
    group by
        uid
    having
        min(score) >= 85
)
union ALL
(
    select
        uid,
        'activity2' as activity
    from
        exam_record er
        left join examination_info ei on er.exam_id = ei.exam_id
    where
        year (start_time) = '2021'
        and ei.difficulty = 'hard'
        and score >= 80
        and timestampdiff (second, er.start_time, er.submit_time) <= ei.duration * 30 ## ei.duration*60*0.5
    group by
        uid
)
order by
    uid;