From: Gregory Stark <stark@enterprisedb.com>
To: <adamtaunowilliams@gmail.com>
Cc: "sql pgsql" <pgsql-sql@postgresql.org>
Subject: Re: Converting from MS Access field aliases
In-Reply-To: <1184272450.4427.35.camel@aleph.whitemice.org> (Adam Tauno
	Williams's message of "Thu, 12 Jul 2007 16:34:10 -0400")
Organization: EnterpriseDB
References: <746273.93291.qm@web54305.mail.re2.yahoo.com>
	<634.1184260980@sss.pgh.pa.us>
	<1184272450.4427.35.camel@aleph.whitemice.org>
Date: Thu, 12 Jul 2007 23:00:22 +0100
Message-ID: <878x9l705l.fsf@oxford.xeocode.com>
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"Adam Tauno Williams" <adamtaunowilliams@gmail.com> writes:

> "AS" works in Informix, and I believe, in DB2 as well.  So it is at
> least pretty common;  I'm not saying it is correct.  Since Informix
> predates M$-SQL they at least didn't invent it.

AS works in Postgres too. But the defined aliases are only in the resulting
output columns, not in scope for the where clause. In fact the expressions
used aren't even evaluated for rows which don't match the where clause which
is pretty important if those expressions are subqueries or volatile functions.

-- 
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com