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Re: weird structure

From: Renato De Giovanni <rdg(at)viafractal(dot)com(dot)br>
To: pgsql-sql(at)postgresql(dot)org
Subject: Re: weird structure
Date: 2000-08-24 22:15:35
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-sql
Yes, Ryan, the idea is to use only one row with all attributes in it.

The structure I described is easy to use when you want to know the attributes
of a single person, and in this case your suggestion is the way to go - I knew

I asked the question considering a specific person_id just to simplify. My real
concern is about retrieving data from more than one person in a query.
If attributes were all columns on "person" table, than a "select
specific_fields from person where conditions=..." would do the job perfectly.
But how could I achieve the same result using that different database schema?

> Does it have to be in one row?
> Otherwise, assuming that person_data.d_person_id references person.a_id and
> person_data.d_attribute_id references person_attribute.a_id:
> select a.a_name from person p, person_data d, person_attribute a where
> p.p_name = 'UserYou'reLookingFor' AND p.p_id = d.d_person_id AND
> d.d_attribute_id = a.a_id
> Would return a list of attributes the person has, one per row.
> ----- Original Message -----
> > Consider the following tables/fields:
> > table "person": fields "p_id", "p_name".
> > table "person_attribute": fields "a_id", "a_name".
> > table "person_data": fields "d_person_id", "d_attribute_id",
> > "d_value".
> >
> > Also consider that a person may not have data related to all possible
> > attributes.
> >
> > Using this structure, how could I retrieve in one row with a single
> > select statement all attributes from a person (showing null to
> > attributes that were not registered to him)?
> >
> > Thanks for any suggestion,
> > --
> > Renato
> > Sao Paulo - SP - Brasil
> > rdg(at)viafractal(dot)com(dot)br

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