While this might work in some caises, it is risky in two ways:
1) You are ordering by whichever field is first. If the column order changes, the order by changes. Stating the column explicitly is safer.
2) The rownum <= upperlimit is not correct as it depends on the order by. This is functionally wrong.
See the Ask Tom article again, in particular the section titled "Pagination with ROWNUM". He shows the
pattern to use is: