Copying data from one table to another

Hi,

I have to copy data from one table to another, and I was wondering if there is 
an easier way to do that than to have a lot of inserts one after another. I 
already looked at the copy command, but what I need should happen in my 
program itself, while the user is waiting, and it's only a partial copy of 
the first table to the second (which has it's own fields, although with 
default values to start with). So the copy command didn't seem an easy (or 
fast) way to do that. Is there a trick to let the INSERT command take more 
than one tuple at once?

Thanks in advance,
Erwin Van de Velde
Student of University of Antwerp,
Belgium