Message-ID: <4C288765.8080604@dreamgnu.com>
Date: Mon, 28 Jun 2010 13:28:37 +0200
From: ced <cedric@dreamgnu.com>
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To: Oliveiros d'Azevedo Cristina <oliveiros.cristina@marktest.pt>,
	pgsql-sql@postgresql.org
Subject: Re: Outer join construction step :strange results
References: <4C28736E.8030409@dreamgnu.com>
	<72B95859322043DF995F2012194B4754@marktestcr.marktest.pt>
In-Reply-To: <72B95859322043DF995F2012194B4754@marktestcr.marktest.pt>
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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
>
>> For every T1 item of a T0 set I want to know if they do or do not have
>> T3 property types and if their values.
>>
>
>>
>> next comes view2 as
>>
>> create view view2 as
>> select T2.fk_T3 as my_id
>> from T2,T1T2
>> where 1=1
>> and T1T2.fk_T1=23456
>> and T1T2.fk_T2=T2.id;
>>
>> This will give me all properties types that the T1 item with id 23456
>> has.
>> let say this query gives me 4 rows.
>>
>
>
> T1T2 is an associative table between items and their property values,
> not types, is this correct?
YES
> If so, I am not realizing why you say that this second view will give
> you all property types. Didn't you mean property values?
no types because T2.fk_T3 is the foreign key to the property types T3
>
> Also, I am not reaching the point of the "1=1" thing. What is the
> propose of it, exactly?
> Isnt that condition always truth ? Maybe I am lacking some sql
> knowledge ...
yes it is allways tru is just a typo trick to have all conditions
aligned so that you can comment them out easily
>
> Thanks in advance for advising me
>
> Best,
> Oliveiros
>
You are to be thanked to getting to my problem

cheers