Message-Id: <m10p8Wq-0003kGC@orion.SAPserv.Hamburg.dsh.de>
From: wieck@debis.com (Jan Wieck)
Subject: Re: [SQL] Order by
To: herouth@oumail.openu.ac.il (Herouth Maoz)
Date: Wed, 2 Jun 1999 12:45:48 +0200 (MET DST)
Cc: michaely@alphanet.net.au, pgsql-sql@postgreSQL.org
Reply-To: jwieck@debis.com (Jan Wieck)
In-Reply-To: <l03130302b37aaa3d3da3@[147.233.159.109]> from "Herouth Maoz" at
	Jun 2, 99 12:34:42 pm
Content-Type: text

Herouth Maoz wrote:
>
> At 03:48 +0300 on 02/06/1999, Michael Yeung wrote:
>
>
> > Hi all,
> >
> > Is anyone know that if we allow order-by clause in the view structure.
> > If not, how can we take the ordering of the UNION ALL in 2 different bags ?
>
> Correct me if I'm wrong, but ORDER BY shoud not be part of a view, in the
> same way it is not a part of a table. A table is defined as an unordered
> collection of tuples. In any given query, you can define the order of the
> tuples returned. But the table itself is not ordered.
>
> A view should look to the user just like a table. The order of the tuples
> is part of the query, not part of the table, and not part of the view.

    That's all right and I'm not going to allow this just for the
    ORDER BY.  It will be enabled  as  kind  of  a  side  effect.
    Because   view's   can   have   a   GROUP   BY   clause,  the
    rewriter/planner  must  be  able  to  produce   plans   where
    different  left-/righttrees have their own grouping. Grouping
    requires  a  sort  and  thus  sorting  of  subplans  must  be
    supported.

    Why should we deny ORDER BY on views explicitly?


Jan

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