In a relation R(A, B, C), if there is a multi-valued dependency between A and B, what condition should be satisfied?
Question
In a relation R(A, B, C), if there is a multi-valued dependency between A and B, what condition should be satisfied?
Solution
In the context of database normalization, a multi-valued dependency (MVD) exists in a relation R(A, B, C) between A and B if for every instance of A, there are multiple instances of B that are independent of C.
The condition that should be satisfied for a multi-valued dependency A ->> B to exist in a relation R is that for any tuple t1 in R, if there exists a tuple t2 in R such that t1[A] = t2[A], then there must also exist a tuple t3 in R such that t1[A] = t3[A], t2[B] = t3[B], and t1[C] = t3[C].
In simpler terms, if A determines B, then the values of B are independent of the values of C. This means that if we know the value of A, we can determine the value of B, regardless of the value of C.
This condition is used in the Fourth Normal Form (4NF) of database normalization to eliminate redundancy caused by multi-valued dependencies.
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