select union 查询出来的结果，如何按指定顺序输出

如有以下sql语句：

select name from student where id='1003' union all
select name from student where id='1001' union all
select name from student where id='1004'

查询出来的结果顺序是未知的。

现在必须按照一定的顺序显示查询的结果，可以用这样的方法：

select name from (
select name ,2 flag from student where id='1003' union all
select name ,1 flag from student where id='1001' union all
select name ,3 flag from student where id='1004') tem order by flag