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Thread: Bcnf

  1. #1
    Join Date
    Feb 2004
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    Bcnf

    hi

    as part of my revision i have been revising normalisation

    attached is a document which i have normalised to BCNF. can n e 1 tell me whether i have done it correctly or not?

    if not can you tell me where i am going wrong and how to correct it.

    please help me my exams are 2morrow and i really don't want to fail please please please please

  2. #2
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    and here is the document
    Attached Files Attached Files

  3. #3
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    Looks to me like Client No functionally determines Client Name and perhaps Tel No, but it does not determine anything else. The same client could use your taxi service for 2 different journeys.

    What has happened to Job Id in the final version?

  4. #4
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    thanks for that i must have missed that off. is this corrected verion better?
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  5. #5
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    Yes, but now you no longer have the FD Staff No -> Veh Reg No which I think you had before.

  6. #6
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    your right - i have now corrected that- is this correct now

  7. #7
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    here's the doc
    Attached Files Attached Files

  8. #8
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    I still can't see where that FD is separated out into its own table in the 2NF version?

  9. #9
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    can u explain a little more in depth or show me what u mean- i'm still not sure?

  10. #10
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    In a normalised set of relations, all non-key attributes must be dependent directly on the relation key.

    Your first relation has the key {JobID, StaffNo}. Is that right? Can there be 2 records with the same JobID but a different StaffNo?

    Does the Veh Reg No depend on the JobID AND the StaffNo as you have it, or does it depend just on the StaffNo? (It could be either, depending on whether cars "belong" to the Staff or are shared between them).

  11. #11
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    there can't be two relations with the same jobid but different staff no's. and the viechel reg only depends on the staff no's.

    i am rea;;y confused now as of where to go from here? what steps should i take next

  12. #12
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    Create a relation with jobid as the key, and put in it what depends on jobid, like Staff No, start time, drop off point, whatever.

    Create another relation with Staff No as the key, and put in it what depends on Staff No, which is just Veh Reg No.

  13. #13
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    Feb 2004
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    thanks for that- i was feaking out a bit there-

    is this now correct. does this apply for £NF and BCNF?

  14. #14
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    i keep forgetting the attachment... Doooooh!!!!

  15. #15
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    and here is is
    Attached Files Attached Files

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