Re: Identifying candidate keys and primary keys

<noagbodjivictor_at_gmail.com> wrote in message news:fc37fe0e-476b-4a0b-8396-ab81c9a5f4a1_at_u69g2000hse.googlegroups.com...
> Hello guys, this one is for one of my assignments. I want explanations
> and hints only.
>
> I'm still confused with the concepts of candidate keys and primary
> key. We have a patient medication form from an hospital with these:
>
> Heading: Patient number, Full name, Bed number, Ward number, Ward
> name.
> Then a table with this columns: drug number, name, description,
> dosage, method of admin, units per day, start date, finish date.
>
> I have to find all the candidate keys and primary keys. I think
> candidate keys are the minimal superkeys.
>
> I have found {Patient number, Ward number, Ward name}. I have excluded
> {Patient number, Ward number, Ward name, Full name} and {Patient
> number, Ward number, Ward name, Full name, Bed number} which are also
> superkeys but contain more attributes.
>

Can a patient be in more than one ward (at the same time)?

> This means that I have found only one candidate key, and this is also
> the primary key I have found (a composite).
>
> Since the question was "identify all the candidate keys" I thought
> maybe I dont really understand the concepts...
>

http://en.wikipedia.org/wiki/Candidate_key

> thanks for any help.
Received on Sun Apr 13 2008 - 13:05:20 CEST