Re: Identifying candidate keys and primary keys
Date: Tue, 15 Apr 2008 08:01:04 -0700 (PDT)
> We have a patient medication form from an hospital with these:
> Heading: Patient number, Full name, Bed number, Ward number, Ward
> 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 would assume it will make it easier first to define the tables, and then the keys. As the requirements were quite vague, my guess (without prejudice) here. Play with it a bit and see if it leads to an answer.
PatientNumber - Primary key
FirstName \ bad candidate key if two persons have the same name LastName /
WardNumber - Primary key
WardName - candidate key (?) No idea if the name is unique, but it is likely.
PatientNumber --- \
WardNumber --- composite primary key
BedNumber --- /
I could imagine a patient can change the ward during its stay in hospital, so might add StartDate, EndDate pair, but that was not mentioned in the specification.
DrugNumber - Primary key
DrugName - candidate key (?) Is a drug name always unique? DrugDescription
DrugNumber --- composite primary key
I would assume that the same drug can be given through out several periods of time, therefore I put the dates into the PK.
Philipp Post Received on Tue Apr 15 2008 - 17:01:04 CEST