count of subqueries plz..

how to get count(*) of a subquery?
something like

select count(*) from
(select F1,F2,F3 from MyTable)

*above doesn't work.

i cannot change, that subquery, it's coming from somewhere else.

Thank You..

Add table alias:

select count(*) from (select F1,F2,F3 from MyTable) as T