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Go Back  dBforums > General > Database Concepts & Design > Functional Dependency/Minimal Basis Problem

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Old 11-06-09, 15:46
Aurora Aurora is offline
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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 FD’s, and we wish to project those FD’s onto relation S(A,B,C). Give the FD’s that hold in S if the FD’s 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?
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Old 11-07-09, 02:17
Derek Asirvadem Derek Asirvadem is offline
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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.
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