Re: data dependent sequences?

"chester c young" <chestercyoung(at)yahoo(dot)com> wrote in message news:609880(dot)51564(dot)qm(at)web54306(dot)mail(dot)re2(dot)yahoo(dot)com(dot)(dot)(dot)
> >
> > CREATE TABLE items (
> > id INT,
> > typ INT ...
> > PRIMAY KEY (seq,typ));
> >
>
> > id typ
> > ----+-----
> > 1 'a'
> > 2 'a'
> > 3 'a'
> > 1 'b'
> > 4 'a'
> > 2 'b'
>
> you will need to use pre insert trigger since you cannot use column
> references in default expression.
>
> you could use this same trigger to either:
> - create sequences as needed and apply the right one
> - with locking, lookup for last id of typ
> - with locking, keep another table of typ and nextval

Thanks, that summerizes the options nicely.

I noticed that sequences are tables with a single row
that defines the sequence properties. I was hoping
that there was some way of using a sequence with multiple
rows to maintain multiplre sequences in a sngle table,
which would make having a large number of sequences a
little less cluttered, but sounds like I need to implement
that from scratch.