George:
> Natural keys, anyone?
Yes.
(1) A DOT code is a 9-digit string identifying the occupation. The first few digits are significant to identify the categories.
(2) The 2-letter postal abbreviation for state can be used as PK for a USState table. It carries some meaning because you can print this abbreviation to identify the state on a letter and the USPS knows what its signification.
Many lookup tables can use natural keys as PKs if the natural key values are almost set in stone.
Daniel
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