On Nov 23, 2006, at 10:23 AM, Ron Johnson wrote:
> I'm one of those who thinks that a (possibly multisegment) natural
> key *does* exist, and that if you think it doesn't, your design is
> wrong.
I agree, but that doesn't mean you want to be spreading that multi-
field key throughout your database. For example, origination,
destination, flight_number, and date together make a unique key for a
segment of a flight. But that doesn't mean you want to be storing all
that info in every other table in the database that references a
segment. Not only does moving all that data around become non-
trivial, writing all that stuff into all the joins is error-prone
(not to mention a PITA).
--
Jim Nasby jim@nasby.net
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)