oracle中关于null排序的问题

问题描述：
在处理一般的数据记录中，对于数字类型的字段，在oracle的排序中，默认把null值做为
大于任何数字的类型，当然对于varchar2类型的字段，默认也是该处理方式，但是客户
要求排序的过程中，需要把null的字段默认排在前边（从小－－>大）。一般的
order by xxxx，无法解决。

问题解决：
方案1：
可以使用复杂的使用sql：

select * from
(select a.*,rownum as my_sys_rownum from (
select deptid,nvl(BDZNAME,'''' ''''),nvl(VOLLEVEL,''''0''''),ZBRL,nvl(ZBTS, ''''0''''),nvl(FZR,''''0''''),nvl(DEPTIDDES,'''' ''''),nvl(TEL,'''' ''''),nvl(RUNSTATEDES,'''' ''''),nvl(ADDRESS,'''' ''''),BDZID from V_BDZ where  rownum<2000

and ZBRL is null

) a
union
select b.*,rownum+(select count(*) from (
select deptid,nvl(BDZNAME,'''' ''''),nvl(VOLLEVEL,''''0''''),ZBRL,nvl(ZBTS, ''''0''''),nvl(FZR,''''0''''),nvl(DEPTIDDES,'''' ''''),nvl(TEL,'''' ''''),nvl(RUNSTATEDES,'''' ''''),nvl(ADDRESS,'''' ''''),BDZID from V_BDZ where  rownum<2000

and ZBRL is null

)) as my_sys_rownum from (
select deptid,nvl(BDZNAME,'''' ''''),nvl(VOLLEVEL,''''0''''),ZBRL,nvl(ZBTS, ''''0''''),nvl(FZR,''''0''''),nvl(DEPTIDDES,'''' ''''),nvl(TEL,'''' ''''),nvl(RUNSTATEDES,'''' ''''),nvl(ADDRESS,'''' ''''),BDZID from V_BDZ where  rownum<2000

and ZBRL is not null order by ZBRL
) b
)
order by my_sys_rownum desc

方案2：
可以利用oracle中可以对order by中对比较字段做设置的方式来实现：
  如：  ……order by nvl( aaa,''''-1'''')