Let's keep it simple then. What sound business reason is there to not have a primary key constraint on the item master file?Because I control it programmatically and thus I don't need a constraint. Now, technically, that means that I could get two records with the same key (it would require two jobs adding the same item at precisely the same millisecond, but it could conceivably happen). So it depends on the application. If item masters are added by a human being, then I would say the constraint is unnecessary. If they are added in bulk by a batch process, perhaps more of an issue. If you have a process that tends to add duplicate records, then you probably do need it (of course, I'd focus on fixing the process).