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In-Reply-To: <20091031211106.GA9238@miraculix>
References: 
 <A434C531E37AD442815608A769550D80590432A1BC@EGEXCMB01.oww.root.lcl>
	<20091031211106.GA9238@miraculix>
Date: Fri, 6 Nov 2009 14:45:15 -0500
Message-ID: <22431f1b0911061145o39013cfem8d4e7a390f9a9ea@mail.gmail.com>
Subject: Re: how to: refer to select list calculations other places in
	the calculations.
From: the6campbells <the6campbells@gmail.com>
To: Bernd Nawothnig <Bernd.Nawothnig@t-online.de>
Cc: "Little, Douglas" <DOUGLAS.LITTLE@orbitz.com>,
	"pgsql-sql@postgresql.org" <pgsql-sql@postgresql.org>
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SQL (unlike MDX) does not allow you to define an expressions and reference
it elsewhere in the same block by name. As suggested, a hand written or
auto-generated statement can try to refactor the statement by pushing things
into a derived table and the outer blocks refer to the projected item names.
Not only can this make the SQL more readable it can assist some vendors who
internally may not do a great job of common expression factoring. This is
one reason why common table expressions are used.

For example, if you are in report studio, you can copy the data items into
another Bi-Query which you reference from the query that consumes it.



On Sat, Oct 31, 2009 at 4:11 PM, Bernd Nawothnig <
Bernd.Nawothnig@t-online.de> wrote:

> On Wed, Sep 09, 2009 at 08:27:35AM -0500, Little, Douglas wrote:
>
> > I have very complex sql (generated by cognos) I'm porting from
> > Teradata that basically uses column alias in the calculated columns.
> > Is there any way to do this type of thing in Psql?
>
> I use nested subqueries and do the renaming of calculated columns in the
> innermost queries in such cases.
>
>
>
>
> Bernd
>
> --
> Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-sql
>

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<div>SQL (unlike MDX) does not allow you to define an expressions and refer=
ence it elsewhere in the same block by name. As suggested, a hand written o=
r auto-generated statement can try to refactor the statement by pushing thi=
ngs into a derived table and the outer blocks refer to the projected item n=
ames. Not only can this make the SQL more readable it can assist some vendo=
rs who internally may not do a great job of common expression factoring. Th=
is is one reason why common table expressions are used. </div>

<div>=A0</div>
<div>For example, if you are in report studio, you can copy the data items =
into another Bi-Query which you reference from the query that consumes it. =
</div>
<div><br><br>=A0</div>
<div class=3D"gmail_quote">On Sat, Oct 31, 2009 at 4:11 PM, Bernd Nawothnig=
 <span dir=3D"ltr">&lt;<a href=3D"mailto:Bernd.Nawothnig@t-online.de">Bernd=
.Nawothnig@t-online.de</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"PADDING-LEFT: 1ex; MARGIN: 0px 0=
px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">On Wed, Sep 09, 2009 at 08:27:35=
AM -0500, Little, Douglas wrote:<br><br>&gt; I have very complex sql (gener=
ated by cognos) I&#39;m porting from<br>
&gt; Teradata that basically uses column alias in the calculated columns.<b=
r>&gt; Is there any way to do this type of thing in Psql?<br><br>I use nest=
ed subqueries and do the renaming of calculated columns in the<br>innermost=
 queries in such cases.<br>
<br><br><br><br>Bernd<br><font color=3D"#888888"><br>--<br>Sent via pgsql-s=
ql mailing list (<a href=3D"mailto:pgsql-sql@postgresql.org">pgsql-sql@post=
gresql.org</a>)<br>To make changes to your subscription:<br><a href=3D"http=
://www.postgresql.org/mailpref/pgsql-sql" target=3D"_blank">http://www.post=
gresql.org/mailpref/pgsql-sql</a><br>
</font></blockquote></div><br>

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