Re: update set x=(subquery on same table)

NM, figured it out :)

update nodes set parent_id=NULL where id in (select
n1.id from nodes n1 left join nodes n2 on
n1.parent_id=n2.id where n2.id is null);

CSN

--- CSN <cool_screen_name90001(at)yahoo(dot)com> wrote:
>
> That does the trick. I'd also like to figure out a
> way
> to set all parent_ids to NULL if no parent row can
> be
> found. I haven't been able to figure it out so far.
>
> Thanks,
> CSN
>
>
> --- Martijn van Oosterhout <kleptog(at)svana(dot)org>
> wrote:
> > On Fri, Feb 13, 2004 at 12:18:14AM -0800, CSN
> wrote:
> > > I'm trying to do:
> > >
> > > update nodes n1 set n1.parent_id=(select n2.id
> > from
> > > nodes n2 where n2.key=n1.parent_id);
> > >
> > > To set parent_id to the id of the parent (rather
> > than
> > > the key). Would UPDATE FROM fromlist work? I
> > couldn't
> > > find any examples of it's use.
> >
> > See the online help:
> >
> > # \h update
> > Command: UPDATE
> > Description: update rows of a table
> > Syntax:
> > UPDATE [ ONLY ] table SET col = expression [, ...]
> > [ FROM fromlist ]
> > [ WHERE condition ]
> >
> > So try:
> >
> > update nodes set parent_id=n2.id FROM nodes n2
> where
> > n2.key=nodes.parent_id;
> >
> > Unfortunatly you can't alias the table you're
> > updating, but you can alias
> > the rest.
> > --
> > Martijn van Oosterhout <kleptog(at)svana(dot)org>
> > http://svana.org/kleptog/
> > > (... have gone from d-i being barely usable even
> > by its developers
> > > anywhere, to being about 20% done. Sweet. And
> the
> > last 80% usually takes
> > > 20% of the time, too, right?) -- Anthony Towns,
> > debian-devel-announce
> >
>
> > ATTACHMENT part 2 application/pgp-signature
>
>
>
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