SELECT stu.*,s.s_score,c.c_name,a.ascore FROM student stu, score s,(SELECT s_id,AVG(s_score) ascore FROM score GROUP BY s_id) a,course c WHERE stu.s_id=s.s_id AND a.s_id =stu.s_id AND c.c_id =s.c_id ORDER BY a.ascore DESC
