Even in this scenario it’s feasible for standards to change. ISBN-15 becomes a thing and suddenly you have books that never get an ISBN-13 so your primary key constraints cause an error for trying to insert a null. Granted, you can see a lot of these changes coming but again, they come on a schedule you don’t control.
Even in this scenario it’s feasible for standards to change. ISBN-15 becomes a thing and suddenly you have books that never get an ISBN-13 so your primary key constraints cause an error for trying to insert a null. Granted, you can see a lot of these changes coming but again, they come on a schedule you don’t control.