To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: "Jim C. Nasby" <jnasby@pervasive.com>, Antoine <melser.anton@gmail.com>,
	pgsql-performance@postgresql.org
Subject: Re: OT - select + must have from - sql standard syntax?
References: <92d3a4950606130543y2aab73d8sbbbf04aee328b41f@mail.gmail.com>
	<20060613210246.GA34196@pervasive.com>
	<19096.1150253069@sss.pgh.pa.us>
In-Reply-To: <19096.1150253069@sss.pgh.pa.us>
From: Greg Stark <gsstark@mit.edu>
Organization: The Emacs Conspiracy; member since 1992
Date: 14 Jun 2006 00:15:30 -0400
Message-ID: <87wtbkcqzh.fsf@stark.xeocode.com>
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Tom Lane <tgl@sss.pgh.pa.us> writes:

> The spec does require a FROM clause in SELECT (at least as of SQL99, did
> not check SQL2003).  However, it's clearly mighty useful to allow FROM
> to be omitted for simple compute-this-scalar-result problems.  You
> should respond to the Oracle guy that "SELECT whatever FROM dual" is not
> in the standard either (certainly the spec does not mention any such
> table).  

Well you could always create a "dual", it was always just a regular table. We
used to joke about what would happen to Oracle if you inserted an extra row in
it...

Oracle used to always require FROM, if it has stopped requiring it then that's
new. I had heard it had special-cased dual in later versions to avoid the
table access overhead, I suspect these two changes are related.

-- 
greg