试卷表和考试记录表内连接 内连接还可以写作:join examination_info using(exam_id); SELECT tag, difficulty, round((sum(er.score) - max(er.score) - min(er.score)) / (count(er.score)-2), 1) as clip_avg_score FROM examination_info ei JOIN exam_record er ON ei.exam_id = er.exam_id WHERE tag ="SQL" and difficulty = "hard"...