Select * from ( Select etc..)

Hello,
I am just wondering how I can select from a generated dataset.
ex.
  Select * from (
    select first, last from staff where salary > 12000
   union
    select first, last from staff where salary < 50000
   )
  order by last

I just took a class in oracle and I thought I remember doing just such a
thing. I know that Oracle does a lot of non-standard sql stuff but it
seems that this would be part of the standard.... I read through the to-do
list to see if it is somthing that is being worked on. But that just
stumped me....   What is this sort of thing called? selecting from a
generated dataset and is it somthing that is being worked on. Or is it
just somthing that I am making up in my head..


Thanks
    Jeff Post
University of Wisconsin - Milwaukee