Question

Suppose a relation looks like this: CUSTOMER(CustID*, CustName, DateOfBirth, City, CityPopulation)

Assume that City determines the CityPopulation.

Assuming that all non key attributes are non-atomic and single-valued,

what normal form is the relation in?

a. 0NF b. 1NF c. 2NF d. 3NF

Answer 1

Functional dependencies :-

CustID ->CustName,DateOfBirth,City,City population.

It is given that City determines the CityPopulation.

City ->CityPopulation

First of all,A relation is said to be in 1NF if all of its attributes are single valued.

and it is given that all attributes are single-valued so,the given relation CUSTOMER is in 1NF.

Let's see if relation is in 2NF or not?

A partial dependency is functional dependency in which left side is proper subset of candidate key and it's right side are non prime attributes.

A relation is said to be in 2NF if there are no partial dependency in it.

Since,there is only candidate key (CustID)which is composed of only 1 attribute.so,there can't be any proper subset of candidate key.if there is proper subset of candidate key then there is no chance of having partial dependency.

Since,there is no partial dependency the relation CUSTOMER is in 2NF.

Let's if relation is in 3NF or not?

A relation is said to be in 3NF if all functional dependencies has its left side as super key or it's right side as prime attributes(attributes that are part of candidate key).

Clearly,we have functional dependency (City->CityPopulation) which has neither it's left side as super key nor it's right side as prime.

So,the relation CUSTOMER is not in 3NF.

Therefore,The highest normal form relation CUSTOMER satisfies is 2NF.

option c).2NF is right option.