四表联合查询

SELECT class_t.classname, t1.studentname, t1.totalscore
FROM
    class_t ,
    (SELECT student_t.studentid, studentname, classid, SUM(score) totalscore
           FROM student_t ,score_t
              WHERE student_t.studentid = score_t.studentid
              GROUP BY student_t.studentid, studentname, classid) t1,
    (SELECT classid, MAX(totalscore) totalscore
    FROM  
    (SELECT student_t.studentid, studentname, classid, SUM(score) totalscore
           FROM student_t ,score_t
              WHERE student_t.studentid = score_t.studentid
              GROUP BY student_t.studentid, studentname, classid) t1
    GROUP BY classid) t2
WHERE class_t.classid = t1.classid
AND t1.classid = t2.classid
AND t1.totalscore = t2.totalscore

上面的有点问题，这是改过的。
小弟初学，很多习惯还不是很好，有什么问题请各位多多指点。

这个t1，上下两个是一样的，怎样才能不重写