Simple sql question, I think.

Is there a way to take the average of a group of averages in a sql
statement?

So for instance:

select a, b, avg( c) from T group by a, b;

-- That finds the average of each group a,b.

Now how to take the average of those averages? I can create a view I
suppose, but I'm curious to know if there was a way to do it without
resorting to making a view?

thanks.

.