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Unformatted text preview: Z". For example, we may have "(S#, P#) Qty" and thus "(S#, P#) S#, Qty" (by augmentation rule). However, from "(S#, P#) S#, Qty", we can NOT derive "P# Qty". W hich functional dependency to remove? Suppose we have a relation R(ABC) with functional dependencies F = {A B, B C, A C}. We can see that "A C" can be derived from "A B" and "B C". Here we should remove "A C" when we construct minimal cover for F, since "A C" can be derived from the remaining functional dependencies. If we removed "A B" or "B C" instead of removing "A C", we would not be able to rederive the removed one from the remaining fds. So the idea is to remove the fds which are derivable from the others, and keep those fds used in the process of derivation....
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This note was uploaded on 01/25/2010 for the course CSC 4402 taught by Professor Staff during the Spring '08 term at LSU.
 Spring '08
 Staff
 Databases

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