key and beats the hell out of a generic "id" field.However, if you have an alphanumeric field, let's say varchar 50, and it's guaranteed that it will never have a duplicate, then THAT is a natural primaryBefore ANYONE continues to insist that a serial id column is good, consider the case where the number of tuples will exceed a bigint.Don't say it cannot happen, because it can.
Except for it being fatter. 400 bits wide instead of 64. But that, too, is simply another consideration to evaluate.
David J.
