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  1. #1
    Join Date
    Nov 2009

    Functional Dependency/Minimal Basis Problem

    I have a question about this:

    Suppose we have relation R(A, B, C, D, E) , with some set of FDs, and we wish to project those FDs onto relation S(A,B,C). Give the FDs that hold in S if the FDs for R are:

    A-> D, BD->E, AC->E, and DE->B

    When finding closure for all of them, I find that there is no minimal basis for S, though am not sure. What do you guys think?

  2. #2
    Join Date
    Mar 2009
    Sydney, Australia
    That's right.

    But the issue is, you may have normalised the FDs in the relations (each within themselves) but you haven't normalised the FDs (all columns and FDs) together; you haven't normalised the relations together, to produce a database. When you do that, the conflicts will disappear.
    Derek Asirvadem (Formerly DerekA)
    Information Architect / Senior Sybase DBA
    Copyright 2009 Software Gems Pty Ltd

    I answer questions from the Original Poster only. If you have a genuine question, as the moderators have requested, start a new thread.

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