Re: Reasons for creating linking tables?

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От Machiel Richards
Тема Re: Reasons for creating linking tables?
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Msg-id 1289824110.2729.77.camel@machielr-laptop
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Ответ на Re: Reasons for creating linking tables?  ("Oliveiros d'Azevedo Cristina" <oliveiros.cristina@marktest.pt>)
Ответы Re: Reasons for creating linking tables?  (Lew <noone@lewscanon.com>)
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Thank you,


that is exactly how I was looking at it too, however the specific database have loads of these so I thought that maybe there is a reason for it and I might be missing something due to limited experiences.



-----Original Message-----
From: Oliveiros d'Azevedo Cristina <oliveiros.cristina@marktest.pt>
To: Machiel Richards <machielr@rdc.co.za>, pgsql-novice@postgresql.org
Subject: Re: [NOVICE] Reasons for creating linking tables?
Date: Mon, 15 Nov 2010 12:26:19 -0000



    I would like to get the point of view from you guys out there who has had a lot of database experience.

    While busy looking into a database that have a lot of issues I have found the following  scenario :

        - Let's call the 3 tables in question tables a,b & c.
        - Currently table a has got a FK referencing table b
        - table b contains only 1 field called id which is the PK and also a FK referencing table c
        - table c is once again a table with a couple of fields.


    My question on this is, why create the linking table?

    Surely the linking table can be removed and the data referenced directly between tables a & c?

    Is there a specific reason why this would need to be done?
 
* In this specific case, frankly, I can't see none...
It seems you have a relation Many-to-One between table a and c.
I usually place an associative table in the middle when I have a many-to-many relationship, which is not the case.
 
In this scenario I would consider table b superfluous (specially when it has no other fields except its ID) and short circuit it.
 
That's my oppinion
 
Best,
Oliver


       

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