Temporary table instead of repeated joins

hello all,

in my program I have to check for a certain combination of data before I 
make an insert. The check is a select statement with a join and a 
function call. Now, I wonder if I could gain performance if I would 
create a temporary view that contained this join and the function call 
and the other constraints. There will be frequent inserts into the 
underlying tables so I can't use a real cache that is only updated once 
in a while (say, a temporary table).

So would a select on the view be faster or is the view really just some 
shortcut for the programmer but the database behaviour actually stays 
the same?

Thanks for any hints
Chantal