Question

Which functional dependency holds in given relation R (A, B,

Q: Answer-Which functional dependency holds in given relation R (A, B, C) and why?

AB -C satisfies condition1 all the values of AB are unique, but C-B does not satisfy any of the three conditions C has not unique values, B has not all same values and the value of C is repeated two times 8, 5 then the value of B is not repeated, so option 1 is incorrect. B-C A satisfies condition1, and B- C also satisfies condition1, so option 2 is correct. B-C A satisfies condition1, but A-C does not satisfy any of the three conditions, so option 3 is incorrect. A-C B does not satisfy any of the three conditions, and B- C satisfies condition1, so option 4 is incorrect. Since BC -A B -C holds in above relation, option 2 will be the answer.

C and why?

Read the below passage and answer the questions Functional dependency A B means that B is dependent on A
i.e. from the value of A we can find the value of B from the relation. Therefore, to prove A B holds in a relation, one of the following conditions must be true: Condition1: either all the value of A must be unique Or Condition2: all the value of B must be same Or Condition3: If two or more tuples/rows of the relation have same value for attribute A then there must be also same value for attribute B
i.e. if t1[A] = t2[A] then there must be t1[B] = t2[B].

A 1

B 2

C 3

D 4

E None of these

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