题解 | #分别满足两个活动的人#

(SELECT uid, 'activity1' FROM examination_info ei 
JOIN exam_record er 
ON ei.exam_id=er.exam_id 
WHERE year(start_time)=2021
GROUP BY uid
HAVING min(score)>=85 
)
UNION ALL
(SELECT uid, 'activity2' FROM examination_info ei 
JOIN exam_record er 
ON ei.exam_id=er.exam_id 
WHERE year(start_time)=2021
AND difficulty='hard' AND score>80
 AND TIMESTAMPDIFF(second, er.start_time, er.submit_time)<=duration*30
GROUP BY uid 
)
ORDER BY uid