From: Oliveiros d'Azevedo Cristina <oliveiros.cristina@marktest.pt>
To: ced <cedric@dreamgnu.com>
To: pgsql-sql@postgresql.org
Subject: Re: Outer join construction step :strange results
Date: Mon, 28 Jun 2010 12:10:47 +0100
Message-ID: <72B95859322043DF995F2012194B4754@marktestcr.marktest.pt> (raw)
References: <4C28736E.8030409@dreamgnu.com>
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?
> 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?
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?
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 ...
Thanks in advance for advising me
Best,
Oliveiros
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Cc: oliveiros.cristina@marktest.pt, cedric@dreamgnu.com
Subject: Re: Outer join construction step :strange results
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