题解 | #作答试卷得分大于过80的人的用户等级分布#

SELECT level, COUNT(DISTINCT er.uid) level_cnt FROM exam_record er
JOIN user_info ui ON er.uid=ui.uid
JOIN examination_info ei ON er.exam_id=ei.exam_id
WHERE tag='SQL' AND score>80
GROUP BY level 
ORDER BY level_cnt DESC, level DESC