GATE | GATE CS Mock 2018 | Question 59

Consider a database with the following schema:

Person ( name, age, gender )
name is a key
Frequents ( name, pizzeria )
(name, pizzeria) is a key
Eats ( name, pizza )
(name, pizza) is a key
Serves ( pizzeria, pizza, price )
(pizzeria, pizza) is a key

Relational algebra expression for query “Names of all people who frequent only pizzeria’s serving at least one pizza they eat” is

(A)

(B)

(C)

(D) None of the above

Answer: (B)
Explanation: Find names of all people who frequent only pizzerias serving at least one pizza they eat :

Option (B) is correct.
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