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  1. #1
    Join Date
    Apr 2011

    Database Design - Functional Dependencies

    Hi all

    Attached is an exercise from a book that I am having difficulties answering.

    hireDate & carReg are the primary keys. So my question can anyone find any extra functional dependencies other than the ones I have identified below....Modifications also welcome:

    fd1 carReg -> make, model, outletNo, outletLoc
    fd2 custNo -> custName
    fd3 outletNo -> outletLoc
    fd4 model -> make (only if we assume a model name is unique to a make)
    fd5 carReg, hireDate -> make, model, custNo, custName, outletNo, outletLoc

    I'm not sure if the above are correct and I am sure there are more. Please can someone help me finally understand these damned FD's!

    I am sure there are more FD's. For example given the relation, custName -> custNo. But if for arguments sake, another J Smith was added, this wouldn't hold. I know by definition functional dependencies must hold for all time...Therefore custName -> custNo is invalid even for the attached instance of the given relation...Am I correct?

    Please let me know if anything needs more clarification...
    Attached Thumbnails Attached Thumbnails fds.jpg  

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