Suppose relation R(A,B,C,D,E) has the following functional dependencies:A -> BB -> CBC -> AA -> DE -> AD -> EWhich of the following is not a key?B, CAED
Question
Solution
To determine which of the following is not a key, we need to find the closure of each set of attributes and see if it includes all attributes in the relation.
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For B, C: The closure of B, C is {B, C, A}. It does not include all attributes in the relation R(A,B,C,D,E). So, B, C is not a key.
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For A, E, D: The closure of A, E, D is {A, B, C, D, E}. It includes all attributes in the relation R(A,B,C,D,E). So, A, E, D is a key.
Therefore, B, C is not a key.
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