returned multiple data from function

Hello.

Example:

select function getmylogs (inet) returns set of mylogs
as 'select mylogs.* from mylogs
where $1 = mylogs.local_ip'
language 'sql';

Returns:

?column?
--------
136538048
136538048
136538048
136538048
136538048
136538048
136538048

etc.

It not the table from database.

or nex example:

create function gelinvoice (int4) returns ?__?
as ' SELECT Invoice.Num, Invoice.Date, Buyer.Name
FROM Invoice, Buyer
WHERE Invoice.BuyerID=Buyer.ID AND Buyer.Num-$1
ORDER BY Buyer.Name'
Language 'sql';

What in that case it is necessary to write in ?__? ?
Or if it is necessary to return result of select of the temporary table?

Maxim.
http://virus.e-foto.ru