Path: text.usenetserver.com!out01a.usenetserver.com!news.usenetserver.com!in02.usenetserver.com!news.usenetserver.com!postnews.google.com!j44g2000cwa.googlegroups.com!not-for-mail From: "Solomon_Man" Newsgroups: comp.databases.oracle.server Subject: Re: Theory Questions concerning MVD and Functional Dependency..... Date: 12 Dec 2006 13:51:48 -0800 Organization: http://groups.google.com Lines: 76 Message-ID: <1165960308.058741.93130@j44g2000cwa.googlegroups.com> References: <1165933367.087896.262660@f1g2000cwa.googlegroups.com> <1165944291.728656.317640@j44g2000cwa.googlegroups.com> <1165945534.581169.119110@79g2000cws.googlegroups.com> <1165946990.340434.283460@f1g2000cwa.googlegroups.com> <1165949249.828359.97540@l12g2000cwl.googlegroups.com> <1165958789.280238.256150@16g2000cwy.googlegroups.com> NNTP-Posting-Host: 208.46.47.5 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" X-Trace: posting.google.com 1165960313 18115 127.0.0.1 (12 Dec 2006 21:51:53 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Tue, 12 Dec 2006 21:51:53 +0000 (UTC) In-Reply-To: <1165958789.280238.256150@16g2000cwy.googlegroups.com> User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322),gzip(gfe),gzip(gfe) Complaints-To: groups-abuse@google.com Injection-Info: j44g2000cwa.googlegroups.com; posting-host=208.46.47.5; posting-account=kLePdg0AAAA1K_S794Fa_4gyG8Sgcp-i Xref: usenetserver.com comp.databases.oracle.server:419058 X-Received-Date: Tue, 12 Dec 2006 16:51:53 EST (text.usenetserver.com) 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@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" 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.