用SQL抽出每科學期進步最多的學生

各位同工:

請問如何修改以下SQL抽出每科學期進步最多的首3名學生，謝謝.

select
a.CLASSLVL,
a.CLASSCODE,
a.CLASSNO,
b.CHNAME,
e.en_des 'Subject',
e.ch_des '科目',
c.SYSSCORE 'T1_Score',
d.SYSSCORE 'T2_Score',
T2_SCORE-T1_SCORE 'Differenct'
from wsadmin.VW_STU_LATESTSTUSCHREC a
join wsadmin.TB_STU_STUDENT b
on a.SUID = b.SUID and a.STUID = b.STUID and a.SCHYEAR = ? and a.CLASSLVL = ?
join wsadmin.TB_ASR_SUBJASSESSDATA c
on a.SUID = c.SUID and a.STUID = c.STUID and a.SCHYEAR = c.SCHYEAR and
c.TIMESEQ = 1100 and c.SYSSCORE is not null
join wsadmin.TB_ASR_SUBJASSESSDATA d
on a.SUID = d.SUID and a.STUID = d.STUID and a.SCHYEAR = d.SCHYEAR and
d.TIMESEQ = 1200 and c.SUBJCODE = d.SUBJCODE and c.MOI = d.MOI and
d.SYSSCORE is not null
left outer join tb_hse_common e
on a.suid=e.suid and c.subjcode=e.code_id and e.tb_id='SBJ'
order by 1, 5, 9 desc

 

由於進步分差沒有排名這項數據，所以未能修改SQL以抽出首3名學生。
但老師可以使用以下SQL語句，以減少沒有進步的數據: