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Re: extension for sql update

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Susanne Ebrecht <miracee(at)miracee(dot)de>, pgsql-hackers(at)postgresql(dot)org, pgsql-patches(at)postgresql(dot)org
Subject: Re: extension for sql update
Date: 2006-07-27 13:11:48
Message-ID: 200607271311.k6RDBmH27064@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Tom Lane wrote:
> much anything that can generate a row.  The patch as you have it
> provides nothing more than syntactic sugar for something people can do
> anyway.  The reason people want this syntax is that they expect to be
> able to write, say,
> 
> 	UPDATE mytab SET (foo, bar, baz) =
> 	    (SELECT alpha, beta, gamma FROM othertab WHERE key = mytab.key);
> 
> and with something like that you can't break apart the row-valued
> expression in the grammar.  So in reality the feature has to propagate
> much further into the backend than this.

That UPDATE example is interesting because I remember when using
Informix that I had to do a separate SELECT statement for each UPDATE
column I wanted to update.  I didn't realize that you could group
columns and assign them from a single select --- clearly that is a
powerful syntax we should support some day.

-- 
  Bruce Momjian   bruce(at)momjian(dot)us
  EnterpriseDB    http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

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