Re: easy way to insert same value into 2 columns

On Thursday 16 October 2003 11:11, Sebastian Boeck wrote:
> Csaba Nagy wrote:
> > For your specific question I don't know the answer.
> >
> > For this particular case you could use:
> >
> > create table your_table (
> > id integer default nextval ('public.zeit_id_seq'::text),
> > pos_id integer default currval ('public.zeit_id_seq'::text),
> > ...
> > );
> >
> > That would work fine as long as you use inserts which don't specify id
> > if pos_id is not specified (otherwise the currval will throw you an
> > error cause it cannot be called without nextval being called).
> >
> > HTH,
> > Csaba.
>
> Thanks a lot, but is it save to use?

Not really.

> Do i always get the same value, even if an other insert is changing
> the sequence >public.zeit_id_seq< just at the same time?

Other processes can't interfere - the whole point of sequences is that they
are safe for this sort of thing.

Where you will have problems is that if one of the developers decides it's
more efficient to process fields backwards (zzz...pos_id, id) rather than
forwards (id, pos_id, ...zzz) then it will break.

Use a trigger here. If nothing else so you can stop people like me doing:

INSERT INTO your_table (id,pos_id) VALUES (-1,DEFAULT);

--
Richard Huxton
Archonet Ltd