Are circular REFERENCES possible ?

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От Denis Bucher
Тема Are circular REFERENCES possible ?
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Msg-id 5.1.0.14.0.20010807114609.00a18490@mail.niftycom.com
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Ответы Re: Are circular REFERENCES possible ?  ("Grigoriy G. Vovk" <grigoriy.vovk@linustech.com.cy>)
Re: Are circular REFERENCES possible ?  (David Lizano <david.lizano@izanet.com>)
Re: Are circular REFERENCES possible ?  ("Josh Berkus" <josh@agliodbs.com>)
Re: Are circular REFERENCES possible ?  (Gary Stainburn <gary.stainburn@ringways.co.uk>)
Список pgsql-sql
Hello !

I have a case where I wanted to do circular REFERENCES, is this
impossible ?

Just an example where it would be useful :

We deliver to the *shops* of our *customers*.
We have therefore two tables : - customers (enterprise, financial information, and so on...) - shop (with a name,
street,phone number, name of manager)
 

Now, each shop REFERENCES a customer so that we know
to which customer belongs a shop.

AND, each customer has a DEFAULT shop for deliveries, i.e. most
customers only have one shop, or a main shop and many small ones.
Therefore a customer should REFERENCES the 'main' or 'default' shop.

Which leads to :

CREATE TABLE shops ( id_shop SERIAL PRIMARY KEY, id_cust integer REFERENCES 
customers, .......)
CREATE TABLE customers ( id_cust SERIAL PRIMARY KEY, id_defaultshop integer 
REFERENCES shops, .......)

But this doesn't work ! Postgres complains like "ERROR:  Relation 
'customers' does not exist"
when creating 'shops'.

Someone told me I should create a third table, ok, but in this case I loose 
the total
control about my logic... Do you have a suggestion ?

Thanks a lot in advance !

Denis



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