From: | Rod Taylor <pg(at)rbt(dot)ca> |
---|---|
To: | Robert Treat <xzilla(at)users(dot)sourceforge(dot)net> |
Cc: | pgsql-hackers(at)postgresql(dot)org, Bruce Momjian <bruce(at)momjian(dot)us>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Susanne Ebrecht <miracee(at)miracee(dot)de>, pgsql-patches(at)postgresql(dot)org |
Subject: | Re: [HACKERS] extension for sql update |
Date: | 2006-07-31 00:38:30 |
Message-ID: | 1154306310.24186.236.camel@home |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers pgsql-patches |
On Sun, 2006-07-30 at 20:20 -0400, Robert Treat wrote:
> On Thursday 27 July 2006 09:28, Bruce Momjian wrote:
> > Tom Lane wrote:
> > > Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > > > Tom Lane wrote:
> > > >> UPDATE mytab SET (foo, bar, baz) =
> > > >> (SELECT alpha, beta, gamma FROM othertab WHERE key = mytab.key);
> > > >
> > > > 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.
> > >
> > > No question. The decision at hand is whether we want to look like
> > > we support it, when we don't yet. I'd vote not, because I think the
> > > main use-case for the row-on-the-left syntax is exactly this, and
> > > so I fear people will just get frustrated if they see it in the
> > > syntax synopsis and try to use it.
> >
>
> I'm not a big fan of implementing partial solutions (remember "left-joins are
> not implemented messages" :-) way back when) , however in my experience with
> this form of the update command, the primary usage is not to use a subselect
> to derive the values, but to make it easier to generate sql, using a single
I disagree. UPDATE mytab SET (foo, bar, baz) =(SELECT ...) is the
specifications way of doing an update with a join. That is its primary
purpose.
UPDATE ... FROM is a PostgreSQL alternative to the above.
--
From | Date | Subject | |
---|---|---|---|
Next Message | Robert Treat | 2006-07-31 01:10:45 | Re: 64-bit integers for GUC |
Previous Message | Robert Treat | 2006-07-31 00:20:17 | Re: [HACKERS] extension for sql update |
From | Date | Subject | |
---|---|---|---|
Next Message | Alvaro Herrera | 2006-07-31 01:14:11 | Re: READ ONLY transaction documentation error |
Previous Message | Robert Treat | 2006-07-31 00:20:17 | Re: [HACKERS] extension for sql update |