sqlplus int数字第一位是0，如何保留

原代码如下 想返回学生学号（STUDENT.snum）
其中有：
0148
1234
等，都是四位int，不能改变原表格式，如何显示完整的学号？谢谢。在线等
SELECt STUDENT.snum
FROM STUDENT, ENROLLED
WHERe STUDENT.snum = ENROLLED.snum
GROUP BY sname
HAVINg COUNT(ENROLLED.snum)>1;

SELECt lpad(STUDENT.snum,4,0)

FROM STUDENT, ENROLLED
WHERe STUDENT.snum = ENROLLED.snum
GROUP BY sname
HAVINg COUNT(ENROLLED.snum)>1;

不明白啊 = =！