Posted by bbcrock on 03/04/07 05:00

I have three tables with a relationship I've never worked with
before. Can anyone suggest/comment on the best way to create a third
normal form relationship between these tables?

The tables basically are:

TRAIN (TRAIN_ID and 15 columns about train specs, etc)
TRUCK (TRUCK_ID and 12 columns about truck specs, etc)
TRANSPORTATION_ITEM
This table has, among others, two columns, TRUCK_ID and TRAIN_ID. If
the truck column is used there can be no data in the train column and
vice versa.

This relationship seems denormalized to me, but I don't remember how
to normalize it. Does anyone know the correct name for this kind of
relationship?

thanks!

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