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

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@svana.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@svana.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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