Re: Should I add a Index Key in this case ?

On Wed, Oct 16, 2019 at 7:36 AM Karen Goh <karenworld(at)yahoo(dot)com> wrote:

> Hi Experts,
>
> I have a use case as follows :
>
> add constraints to the database so that no two reservations for the same
> viewing may refer to the same seat.
>
> So, say I have a primary key like this in the table A:
>
>
> SEAT_id integer NOT NULL GENERATED ALWAYS AS IDENTITY ( INCREMENT 1
> START 1 MINVALUE 1 MAXVALUE 2147483647 CACHE 1 ),
> CONSTRAINT A_pkey PRIMARY KEY (SEAT_id))
> WITH (
> OIDS = FALSE
> )
> TABLESPACE pg_default;
>
> So, basically I would like to create a SEAT_Viewing_Id.
>
> In this case, do I create a Index Key or ?
>
> How should I construct or rather alter my table A to accomodate this
> SEAT_Viewing_Id ?
>
> Hope someone can tell me how.
>
> Furthermore, whenever an insertion is done via WebApp, I would have to
> insert the Index key as well or does PostgreSQL will have a way to
> increment the Index key which is the SEAT_Viewing_Id at the same time?
>
> Thanks & regards,
> Karen
>
>
> I'm not sure I understand exactly what you want to do, but it sounds like
you are want to create a second field/column in your table named
"SEAT_viewing_id" and you want that field to auto-increment independently
from the primary key? If so, you can consider the "serial" datatype as
possiblye meeting your needs:
https://www.postgresql.org/docs/current/datatype-numeric.html#DATATYPE-SERIAL

So just `alter table`, to add your new field, and make its datatype
`serial`.

Apologies if I misunderstood your question,
Steve