Message-ID: <4C28A7D0.4060508@dreamgnu.com>
Date: Mon, 28 Jun 2010 15:46:56 +0200
From: ced <cedric@dreamgnu.com>
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To: pgsql-sql@postgresql.org
Subject: Re: Outer join construction step :strange results
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Oliveiros d'Azevedo Cristina wrote:
>
>
>> Oliveiros d'Azevedo Cristina wrote:
>>> Howdy, Cedric .
>>>
>>> Before analysing this problem of yours further, I 'd like you to
>>> kindly clarify me some points, please
>>>
>>>
>>>
>>>>
>>>> I have table following tables  T0,T1,T2,T3, T1T2
>>>> with
>>>> -T0(id, fk_T1)
>>>> -T1(id )
>>>> -T2(id, fk_T3)
>>>> -T1T2(fk_T1,fk_T2)
>>>> -T3 (id)
>>>>
>>>> The table T0 represents sets of T1 items.
>>>> The table T1 represents items.
>>>> The table T3 represents property types.
>>>> The table T2 represents represents property values of a specific type.
>>>>
>>>
>>>
>>> T0.id is not a primary key, is it?
>> all columns with id are Primary keys
>> all columns with fk_T1 are foreign keys
>
>
> Can you specify a little more how you represent T1 item sets with this
> data model?
(T0.id,T0.fk_T1)=(1,234),(1,235),(1,236)

234,235,236 all T1 items and 1 the set of them

> What exactly represents one row from table T0? A pair (id, fk_T1) ? A
> set with just one element?
one item in the set.

>
> Best,
> Oliveiros
>