Re: Constraints and Functional Dependencies
From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Sat, 24 Feb 2007 23:37:16 +0100
Message-ID: <45e0bdad$0$320$e4fe514c_at_news.xs4all.nl>
> ...
> ...
>
> I assume you mean what does a row in TutorFor mean?
Date: Sat, 24 Feb 2007 23:37:16 +0100
Message-ID: <45e0bdad$0$320$e4fe514c_at_news.xs4all.nl>
paul c wrote:
> mAsterdam wrote:
>> paul c wrote:
> ...
>>> Enrolment { StudentId, CourseId } KEY { StudentId, CourseId } >>> >>> (note also that a student may take many courses and that a student >>> may enrol in a course before a teacher is assigned to it) >>> >>> TutorFor { StudentId, StaffId } KEY { StudentId, StaffId } >>> >>> It's possible to enter a row in TutorFor where StaffID stands for a >>> teacher who doesn't teach any course the student is enrolled in. >> >> If it is a base table, yes. That seems a little strange though, >> by way of example - what would a row mean beyond >> what is already in the other tables?
> ...
>
> I assume you mean what does a row in TutorFor mean?
Yes.
> If so, it means a
> student has a particular teacher in some course. Since the schema
> allows different teachers for the same course, that is the only way for
> a student to find out who his teacher for a particular course is.
I see. I overlooked that. Thanks. Received on Sat Feb 24 2007 - 23:37:16 CET