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Re: Partial foreign keys, check constraints and inheritance

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Scott Marlowe wrote:

On Thu, 2005-11-17 at 13:36, Eric E wrote:
Eric E wrote:

maybe you can solve it adding a new col and allow both to contain null values.

if these are not mutually exclusive you can avoid a check if they are
check that if one has a non-null value other has null...
I did think about that, but I disliked the idea of two fields of nulls for every one full field.... maybe it's not as bad a way of doing it as I thought.
BTW, in most cases I have 5+ tables to do this, so that's 4+ fields of
null in each row...Could you use some kind of intermediate join table, so that it pointed
to orders and then products / customers / othermidlevel tables pointed
to it, and so did the problems table?

Clever - that intermediate table sounds like sort of a GUID for every element in the database, along with what table it belongs to, and the problems table points at that GUID. Sounds pretty promising. Thanks for the idea.

EE

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