Re: Understanding candidate key and super key

Joe,

     I map out the table to be as follows: The table will be as follows:

    Lecturer Subject Telephone

        x                a                1
        y                a                1
        y                b                2
        z                b                1

Given the above table, will the (lecturer, subject) and (lecturer,telephone) be the candidate key? The scenario given is that each lecturer can have more than 1 telephone. 2 or more lecturers can teach 1 subject. Also 1 phone can be used by more than 1 lecturer. I am trying to justify the scenario as it is possible that there is other combination. Then, my thought is that for the given scenario, (lecturer,subject,telephone) is the super key. Is this thought correct?

Joe "Nuke Me Xemu" Foster wrote in message ...
>"Low Yew Sing" <slasher_at_singnet.com.sg> wrote in message
 news:89r5dv$jgf$1_at_mawar.singnet.com.sg...
>
>> hi,
>> i have a question concerning candidate key and super key.
>> For example ,
>> if i have a office relation of lecturer, subject and telephone. A
>
>Why? Is lecturer X allowed to talk only about subject Y on phone Z and
>must use phone Z' to talk about subject Y', if the table is as follows?
>
>lecturer subject telephone
>X Y Z
>X Y' Z'
>
>If this is the case, then (lecturer, subject) and (lecturer, telephone)
>are indeed candidate keys.
>
>--
>Joe Foster <mailto:jfoster_at_ricochet.net> Space Cooties!
 <http://www.xenu.net/>
>WARNING: I cannot be held responsible for the above They're coming
 to
>because my cats have apparently learned to type. take me away, ha
 ha!
>
>
Received on Sun Mar 05 2000 - 00:00:00 CET