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  1. #1
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    Sep 2004
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    Unanswered: Finding Minimal Cover for FDs?

    Hi, Does any set of FDs have an unambiguous minimal cover?
    Cheers bro....

  2. #2
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    "Does any set of FDs have an unambiguous minimal cover?"
    .....
    I guess I'm going to be the stupid one .... HUH ?????

  3. #3
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    Sep 2004
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    Sorry about my English if it makes you confused....Im not English speaker.
    I just wanna know that why minimal cover for FDs is not unique.
    Textbook says it's not unique but doesnt give much detail.....

    Cheers...

  4. #4
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    Apr 2004
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    It's not the english that's the problem

    what is "FD"?

    what textbook?

    what "minimal cover"?
    Give a man a fish, you feed him for a day. Club him over the head with a fish, he'll leave you alone.

  5. #5
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    Sep 2004
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    FD is abbr for Functional Dependencies...
    the name of textbook is <database system concept>

  6. #6
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    Again ... It's not the English ... I just don't understand the question or what you are looking for ....

    Gregg

  7. #7
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    Sep 2004
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    Sorry I think I'd better repost this thread to DB concept and design sub-forum...

  8. #8
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    Demonization, let me try a guess : aren't you french ?
    It looks like some fast "french to english" translation to me that some friends of mine could well have made.

    "Dépendances fonctionnelles" and "couverture minimale" do remind me of something, if it is what you're talking about, but I'd have to go deep in my memories in order to help you, I fear...

    Regards,

    RBARAER

  9. #9
    Join Date
    Sep 2004
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    6

    Yes it is!

    Yep, that's what I am talkin' about. However Im not french...sorry
    Again, why minimal cover is not unique for a set of functional dependencies? Any help would be great!

  10. #10
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    I am very familiar with DB concepts and design, but I've never in my life heard about "minimal cover", while "functional dependencies" is one of those oddly vague normalization terms that never seem to mean anything until you've read the rest of the sentence a couple of times.

    Still intrigued though.

    > Textbook says it's not unique but doesnt give much detail...

    What exactly (and without saying "FDs") does the textbook "<database system concept>" say is not unique?

  11. #11
    Join Date
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    Where the Surf Meets the Turf @Del Mar, CA
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    Provided Answers: 1
    > "minimal cover" of what?
    Please compare & contrast minimum cover to maximum cover.
    Please compare & contrast unambiguous minimal cover to ambiguous [minimal | maximimum] cover?"
    You can lead some folks to knowledge, but you can not make them think.
    The average person thinks he's above average!
    For most folks, they don't know, what they don't know.
    Good judgement comes from experience. Experience comes from bad judgement.

  12. #12
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    "Unambiguous" means "unique", D told us that much under cross-questioning.

    Is the textbook "Database System Concepts" by Henry F. Korth and Abraham Silberschatz (McGraw-Hill 2001), described by one Amazon reviewer as "Possibly the least accessible book ever"?

    Demonization, I think a practical example would help us out here. Clearly "minimal cover" is not a database term anyone is familiar with, and "functional dependencies" and their uniqueness or lack of it are not ringing any bells either. However if it refers to unique foreign keys or some such, we may start getting somewhere.

  13. #13
    Join Date
    Sep 2004
    Location
    London, UK
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    For anyone still interested, FDs are explained here:
    clem.mscd.edu/~tuckerp/CSI3310/C14.2.html

    Or if you prefer, here:
    cs.hbg.psu.edu/courses/comp419.taw.s97/rdesign3.html

    Still not quite clear? Never mind, here is a Powerpoint presentation:
    www.cise.ufl.edu/~jhammer/classes/4720-5725/SP03/lectures/lecture_10.ppt

    Now aren't you glad we got that cleared up?


  14. #14
    Join Date
    Aug 2004
    Location
    France
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    Hi WilliamR,

    Thanks for the links you gave. I knew I had heard about these things during my studies, before SQL courses, in a course about "Database Conception"... but I did not remember quite well what it was. Now I do. However, I understand why I had forgotten it...

    Regards,

    RBARAER

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