Re: Question on Primary Keys

Well,

Here is another example , I think it is a little easier to discuss :

Table : USER - USER_ID (PK)

                         USER_NAME

Table : CALENDAR - CALENDAR_ID
                                    USER_ID
                                    .........
                                    .........

I have heard from other sources that both CALENDAR_ID and USER_ID should be the combined primary key for the calendar table. (This is said to be the more formal approach to this type of situation.)

However, it would also make sense to make CALENDAR_ID the PK and make it a unique sequenced number and then have USER_ID as the FK. This way, the CALENDAR_ID could be indexed very easily. Rather than indexing a combination of 2 columns , it seems easier to index a unique sequenced number.

Any thought ?

Raju

"Reinier" <Reinier_Dickhout_at_hetnet.nl> wrote in message news:enJ#kq0NAHA.349_at_net025s...
> If the existence of the user is depending on the existence of an
> organisation unit you should make it a mandatory FOREIGN key, not a
 primary
> key. Primary keys are intended to identify the uniqueness of a record in
 its
> own table, foreign keys are intended to represent relationships between
> different entities.
>
> Reinier.
>
> Jan Lenders <J.Lenders_at_Betuwe.net> wrote in message
> news:8se93i$qm3$1_at_nnrp1.deja.com...
> >
> > > Each USER belongs to an ORG_UNIT.
> > > (a) The USER table can have a combined PK of USER_ID & ORG_UNIT_ID
> > > (b) The USER table can have a PK of USER_ID (some sort of unique
> > > number) and have ORG_UNIT_ID as a FK.
> > >
> > Raju,
> > If the existence of a USER object is dependent on the existence of a
> > ORG_UNIT you should make the ORG_UNIT_ID (foreign key) a primary key in
> > the USER table.
> >
> >
> > Sent via Deja.com http://www.deja.com/
> > Before you buy.
>
>
Received on Mon Oct 16 2000 - 12:05:16 CEST