rob@xxxxxxxxx wrote:
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).

You're not asking a new question, Rob. We've had the UNIQUE keyword on logicals and keyed physicals forever, and not always used it for the simple reason that it added overhead. Should every primary key have a UNIQUE constraint? That's a business decision. But if I choose not to have it, it doesn't make my database design bad. It just means I trust my application and would prefer not to have the extra overhead of the constraint.

You want to make this a "good" vs "bad" decision and its simply not that way. You have to make each decision with the appropriate forethought.


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