sql server 2005 performance: graphic full list where statement

we have twin tables:

• document: id, title, document_type_id, showon_id


• documenttype: id, name


• relationship: documenttype hasmany documents. (document.document_type_id = documenttype.id)

we wish collect list request forms given showon_id.

we twin possiblities:

select documenttype.*
from documenttype
where documenttype.id (
    name graphic document.document_type_id request where showon_id = 42
);

select documenttype.*
from documenttype
where documenttype.id (
    name document.document_type_id request where showon_id = 42
);

our doubt is: improved graphic smaller record set contra retrieving whole list matter walking list initial match. (we speculation that's does ;-))

is opposite different databases, there common answer?

or there improved proceed doing it? (we .net land)