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To: Bruno Wolff III <bruno@wolff.to>
Cc: Christoph Haller <ch@rodos.fzk.de>, pgsql-sql@postgresql.org
Subject: Re: " Adding missing FROM-clause entry for table .... " problem. 
In-reply-to: <20030218141243.GA11505@wolff.to> 
References: <3E521E3F.C5E4251B@rodos.fzk.de> <20030218141243.GA11505@wolff.to>
Comments: In-reply-to Bruno Wolff III <bruno@wolff.to>
	message dated "Tue, 18 Feb 2003 08:12:43 -0600"
Date: Tue, 18 Feb 2003 10:50:25 -0500
Message-ID: <23770.1045583425@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Bruno Wolff III <bruno@wolff.to> writes:
> Christoph Haller <ch@rodos.fzk.de> wrote:
>> AFAIK, statements like
>> DELETE FROM t1 where t1.id = t2.id ;
>> are legal. Could the parser still work on this, if the feature is
>> removed?

> Only if a new syntax is added.

For UPDATE, we actually do have an extension syntax that allows naming
secondary tables explicitly:

	UPDATE target SET ... FROM other-tables WHERE ...

The trouble with extending this to DELETE is that DELETE already uses
the keyword FROM.  Seems like we are stuck with a choice between

	DELETE FROM target FROM other-tables WHERE ...

	DELETE FROM target, other-tables WHERE ...

both of which are bizarre and confusing to my eyes.  I think that MySQL
uses the second form, which I like even less than the first (it obscures
the very fundamental semantic difference between the deletion target and
the other tables).

Or we could go off with a different keyword, perhaps

	DELETE FROM target WITH other-tables WHERE ...

but that doesn't seem to pass the low-astonishment test either.

Comments?  It would not be difficult to implement any of these
alternatives.  <hhg>okay, you think it's so easy, *you* decide
what color it should be</hhg>

			regards, tom lane