Re: Foreign Key normalization question

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От Scott Marlowe
Тема Re: Foreign Key normalization question
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Msg-id dcc563d10809021340i3f67c175yb5b0c5c32c662bac@mail.gmail.com
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Ответ на Re: Foreign Key normalization question  (Matthew Wilson <matt@tplus1.com>)
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On Tue, Sep 2, 2008 at 2:35 PM, Matthew Wilson <matt@tplus1.com> wrote:
> On Tue 02 Sep 2008 04:19:41 PM EDT, Scott Marlowe wrote:
>> If the two subordinate tables ALWAYS have to point to the same place,
>> why two tables?  Can't a customer have > 1 location?  I'm pretty sure
>> IBM has more than one corporate office you could ship things to.
>
> Yeah, so the idea is one customer might have many locations and many
> products.  And at each location, some subset of all their products is
> available.

You could have the product_locations have a custid1 and custid2 fields
that reference the two parent tables, and then a check constraing on
product_locations that custid1=custid2

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