UGC NET CSE | December 2019 | Part 2 | Question: 97

Question

An organization needs to maintain database having five attributes $\textbf{A, B, C, D, E}$. These attributes are functionally dependent on each other for which functionality dependency set $F$ is given as: $\textbf{F}: \{ \textbf{A} \rightarrow \textbf{BC}, \textbf{D} \rightarrow \textbf{E}, \textbf{BC} \rightarrow \textbf{D}, \textbf{A} \rightarrow \textbf{D} \}$. Consider a universal relation $\textbf{R(A, B, C, D, E)}$ with functional dependency set $\textbf{F}$. Also all attributes are simple and take atomic values only.

Identify primary key of table $R$ with functional dependency set $F$

• A. $\textbf{BC}$
• B. $\textbf{AD}$
• C. $\textbf{A}$
• D. $\textbf{AB}$

Answer 1

closure of A={A,B,C,D,E}

Hence A is the primary key of table R.

closure of BC={B,C,D,E}

closure of AD={A,B,C,D,E}

closure of AB={A,B,C,D,E}

primary key is minimal superkey so,A is the primary key