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Re: circular relationships ok?

From: Volker Hetzer <volker.hetzer_at_ieee.org>
Date: Thu, 02 Mar 2006 17:34:06 +0100
Message-ID: <du76pu$t5c$1@nntp.fujitsu-siemens.com>


Alexandr Savinov schrieb:

> Volker Hetzer schrieb:
>> Alexandr Savinov schrieb:

>>> Volker Hetzer schrieb:
>>>> Hi!
>>>> Just in general, are circular relationships something that
>>>> can always be avoided?
>>>> Or, given a model with a circular relationship, possibly
>>>> spanning several tables, is there a way to get rid of them?
>>>
>>> One approach consists in using the concept-oriented data model as
>>> follows.
>>>
>>> 1. Order your tables so that if table A references records from table
>>> B, then A is positioned under B. For example, if an order has a field
>>> with its customer then you position them as follows:
>>>
>>> Customre
>>> |
>>> Order

>> So, what if A references B, B references C and C references A? Ok, I wasn't specific enough.
what if one row (a) of Table A references a bunch of rows in B, each row (b) in B references a bunch of rows in C and each row (c) in C references zero or one row a' in A?
Then a doesn't references itself, it references another row in the same table.
> Now assume that you have a 
> cycle. This means that an element is a member of itself and it is 
> normally interpreted as a non-sense.

In that case it isn't referencing itself, just another object in the same table.

So, maybe it's not a circle but a spiral of an unknown number of turns.

Lots of Greetings!
Volker Received on Thu Mar 02 2006 - 10:34:06 CST

Original text of this message

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