Re: Using table name in column for joining

From: sabrina miller <sabrina(dot)miller(at)gmail(dot)com>
To: Grzegorz Jaśkiewicz <gryzman(at)gmail(dot)com>
Cc: Antonio Goméz Soto <antonio(dot)gomez(dot)soto(at)gmail(dot)com>, pgsql-general(at)postgresql(dot)org
Subject: Re: Using table name in column for joining
Date: 2010-01-05 17:00:51
Message-ID: a646e46a1001050900m2f4189a6ybf278cea72f4a29f@mail.gmail.com
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You can also have inheritance from animal, in such case you can have
partitioned different animals in different tables with their special
attributes in it.

then you will have:

create table animal(
id serial,
name varchar(20),
age integer
);

create table elephant
(some_attr_that_only_have_
elephants varchar(20)
)
INHERITS (animal);

create table monkey
(some_attr_that_only_have_monkey varchar(20)
)
INHERITS (animal);

insert into elephant (name, age, some_attr_that_only_have_elephants)
values ('sophie',15,'lorem');

insert into monkey (name, age, some_attr_that_only_have_monkey)
values ('lory',3,'impsu');

You can look for diferents animals like this:

select name <http://animal.name/> from animal;
select name <http://animal.name/> from elephant;
select name <http://animal.name/> from monkey;

I hope it helps.

2010/1/5 Grzegorz Jaśkiewicz <gryzman(at)gmail(dot)com>

> On Tue, Jan 5, 2010 at 3:30 PM, Antonio Goméz Soto
> <antonio(dot)gomez(dot)soto(at)gmail(dot)com> wrote:
> > Hello,
> >
> > I have a column in a table that contains the name of another table,
> > and the id in that table.
> >
> > I would like to use this in a join statement. Is that possible?
>
> not possible I'm afraid.
>
> But have a look at concept of inheritance for something that might
> suit you. Or just store everything in one table, but add new id to
> each row. That is what other half of the world uses.
>
> Also, when writing queries like that, consider using aliases for table
> name, for instance:
>
> select a.id from animals a;
>
> makes life easier.
>
> hth
>
> --
> GJ
>
> --
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