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Re: [QUESTIONS] using composite types

From: Peter T Mount <postgresdev(at)maidast(dot)demon(dot)co(dot)uk>
To: "Thomas G(dot) Lockhart" <lockhart(at)alumni(dot)caltech(dot)edu>
Cc: Brian Grossman <brian(at)softhome(dot)net>, pgsql-questions(at)postgresql(dot)org, Postgres Hackers List <hackers(at)postgresql(dot)org>
Subject: Re: [QUESTIONS] using composite types
Date: 1998-03-15 13:16:52
Message-ID: Pine.LNX.3.95.980315131414.4646A-100000@maidast (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Fri, 13 Mar 1998, Thomas G. Lockhart wrote:

> > How can I use composite types?
> > If I create two tables like this:
> >         create table A ( a int, b int);
> >         create table D ( a A, b int);
> > I would expect to be able to
> >         insert into D (a.a, a.b, b) values (1,2,3);
> > and
> >         select a.a, a.b, b from D;
> > That doesn't work, at least not with postgresql 6.3.  Is that the way
> > it's supposed to work?  What is the proper way to do it?

I've just tried it here, and it seems that the value to insert into D is
the OID of a row in table A.

> I'm not sure if this is supported. The old tutorial does not have an
> example exactly like this (at least that I could find), but it seems
> like it _should_ work, and the backend accepts the syntax.
> What you want to do can probably be accomplished with inheritance, but
> that only seems to work if you have unique names for more of your
> fields:
>   create table A ( a int, b int);
>   create table D ( c int) inherits (A);
> But, if you try
>   create table D ( b int) inherits (A);
> then the new column in D gets lost without warning!

This would give a table based on the parent table, but I think he was
trying to use table D to refer to values in table A _as_ a type.

[I may be wrong here, but that's what it looks like]

Peter T Mount  petermount(at)earthling(dot)net or pmount(at)maidast(dot)demon(dot)co(dot)uk
Main Homepage:
Work Homepage: Work EMail: peter(at)maidstone(dot)gov(dot)uk

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