I'm designing a new physical data model using a third party tool. When I generate the database creation script automatically it puts 'not null' constraints on the primary keys. I don't have much experience with this particular tool and can't find the correct setting to stop this.

The extra 'not null' constraints are redundant but what would be the problem if I just leave them? For example, would the 'not null' condition be checked twice for every insert or update?

Any ideas? I could always just edit the script...