two queryes in a single tablescan

Hi everybody,

suppose you have a large table tab and two (or more) queryes like this:

SELECT count(*),A FROM tab WHERE C GROUP BY A;
SELECT count(*),B FROM tab WHERE C GROUP BY B;

is there any way to get both results in a single query,
eventually through stored procedure?
The retrieved [count(*),A] ; [count(*),B)] data couldnt fit
on a single table, of course.

The main goal would be to get multiple results while scanning the
table[s] once only
thus getting results in a faster  way.

This seems to me quite a common situation but i have no clue whether a neat
solution can be implemented through stored procedure.

Any hint?

Thank you

Stefano