Question

In a table regarding the entries of students, which among these can be the most appropriate for PRIMARY KEY?

• A. RollNumber
• B. Name
• C. DateofBirth
• D. Age

Hint:

A Primary Key must be unique and NOT NULL.
In exams, look for formal, system-assigned identifiers (e.g., RollNumber, EmployeeID, AadhaarNumber) over natural characteristics (e.g., Name, Age, Date of Birth).

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks to identify the most suitable candidate attribute to serve as the Primary Key for a database table storing student records.

Step 2: Properties of a Primary Key:
An attribute chosen as a primary key must satisfy three critical requirements:
- Uniqueness: No two rows in the table can have duplicate values in this column.
- Non-nullability: The value cannot be empty (NULL) for any record.
- Invariance: The value should remain stable and not change frequently over time.

Step 3: Detailed Explanation:
Let us analyze the four options based on these key requirements:
- RollNumber: Each student in a class or school is assigned a unique, non-null Roll Number. No two students can share the same Roll Number, and a student's roll number remains static throughout the academic term. It fulfills all requirements perfectly.
- Name: It is common for multiple students to have the exact same name (e.g., "Amit Sharma"). Thus, it fails the uniqueness test.
- DateofBirth: Many students can be born on the same calendar day, so it is not unique.
- Age: Countless students will share the same age. Additionally, age is a derived attribute that changes every year, which violates key stability.

Step 4: Final Answer:
Since RollNumber is unique and invariant for each student, it is the most appropriate attribute for a Primary Key.
Hence, option (A) is the correct choice.