with target_user as (#先是筛选特定的用户 select b.uid, avg(b.score) from examination_info a left join exam_record b on a.exam_id=b.exam_id inner join user_info c on b.uid=c.uid and c.level=7 where a.tag='SQL' and a.difficulty='hard' group by b.uid having avg(b.score)>80 ) #接下来连接三个表,因为exam_record和practice_...