Re: Theory Questions concerning MVD and Functional Dependency.....

Everyone,
Thanks for the help. Especially EscVector and vnr1995.

I answered the question correctly on the test.

I put what I felt was correct but was not 100% certain of it.

Though I missed more on the third problem concerning the NF4, but I figured it was mostly a wash anyways. Thats what worried me the most. I know why it is not in normal form 4 and why it has a MVD, so I have learned from my mistake and I can now put this class behind me.

I appreciate all the help,
Thanks so much,
Chris

EscVector wrote:
> Solomon_Man wrote:
> > So,
> > With all the fun aside.
> >
> > Can someone in laymans terms please explain to me MVD. Please include
> > examples.
> >
> > I have looked on line and there are many examples but none have
> > "clicked".
> >
> > I may be making this hard, actually I should say I know I am making
> > this hard but I would like to understand this. The class at this point
> > means nothing but I would really like to fully understand what a MVD is
> > and be able to identify one.
> >
> > Thanks,
> > Chris
> >
> >
> > vnr1995_at_gmail.com wrote:
> > > The contrapositive of that statement is: If it is not possible for A to
> > > determine B, A multidetermines B (TRUE or False)
> > >
> > > This is true.
> > >
> > >
> > >
> > > On Dec 12, 11:45 am, "Solomon_Man" <cmgra..._at_gmail.com> wrote:
> > > > > > If A does not multidetermine B, it is still possible for A to determine
> > > > > > B. (TRUE OR FALSE).
>
> The answer is TRUE.
>
> The question as I read it is "can A determine B even if B is not a set
> or list?"
> Ask yourself, can A have a one-to-one relationship with B?
> The answer is YES or in your case, TRUE.
>
> If A --->>B does not equal true
> Then it is still possible for
> A-->B
>
> A multivalued dependency means that If you know one attributes value,
> you can always determine another attribute's set value. Relational
> theory uses a double headed arrow to illustrate this relation
> (A--->->B). This means A determines multiple Bs. If you know your
> teacher's name, you can determine his/her students. The student list
> is the "MultiValue". A functional dependency that is not multivalued
> is a one-to-one relationship. (A--->B). This means that A determines
> s B. If I know your student ID, I can determine your first_name.
>
> 4NF eliminates multiple multivalued dependencies within a table by
> splitting the table into multiple tables. The classic example for
> 4NFis Department, job, part where multiple parts are used by multiple
> departments for multiple jobs. Adding or removing a part to a
> department or job requires multiple rows to be touched. Breaking this
> out into a parts table and a jobs table keyed with department fixes
> this problem.
Received on Tue Dec 12 2006 - 15:51:48 CST