how to use count(*) in "group by" queries

I am trying to use count(*) to prevent queries from executing that are blowing out memory. The query comes in two forms:
(1) select a, b, c, d from x, y, z where...;
which I can count first like this:
select count(*) from x,y,z where...; ==> easy enough

The other form is:
(2) select count(*), a, b, max(c), max(d) from x,y,z where... group by
a,b;
this query already has a count(*), which counts the number of rows in each group. How can I count the number of groups that will be returned without actually doing the full query?

Thanks,
Martin Received on Tue Nov 21 2006 - 09:30:50 CST