Question
Data Science and Artificial Intelligence Question on Relational Algebra
Consider a database that includes the following relations :
Defender(name, rating, side, goals)
Forward(name, rating, assists, goals)
Team(name, club, price)
Which ONE of the following relational algebra expressions checks that every name occurring in Team appears in either Defender or Forward, where Φ denotes the empty set ?
A
Пname (Team) \ (Пname (Defender) ∩ Пname (Forward)) = Φ
B
(Пname (Defender) ∩ (Пname (Forward) \ Пname (Team) = Φ
C
Пname (Team) \ (Пname (Defender) ∪ Пname (Forward)) = Φ
D
(Пname (Defender) ∪ (Пname (Forward) \ Пname (Team)) = Φ
Answer
Пname (Team) \ (Пname (Defender) ∪ Пname (Forward)) = Φ
Explanation
Solution
The correct option is (C) : Пname (Team) \ (Пname (Defender) ∪ Пname (Forward)) = Φ.