Re: Identifying candidate keys and primary keys

From: Brian Selzer <>
Date: Sun, 13 Apr 2008 07:05:20 -0400
Message-ID: <5OlMj.19955$>

<> wrote in message
> 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...

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

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