A Primary Key in RDBMS must be: MCQ with Answer and Explanation

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A Primary Key in RDBMS must be:

A. Always a foreign key

B. Duplicate values allowed

C. Unique and not null

D. Can have null values

Answer: Option C

Solution (By JKSSB Mock Tests)

A primary key uniquely identifies each record and cannot contain null values.

This question belongs to: Computer Database Management System (DBMS)

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Practice More Database Management System (DBMS) Questions

Question #1

Which of the following describes an 'Entity' in database terms?

A. An action or method inside code.

B. A line connecting tables.

C. A physical server rack.

D. A real-world object or concept that is distinguishable from other objects and about which data is stored.

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Correct Answer: Option D

Explanation:
An Entity is a distinguishable real-world object, place, person, or concept captured within a database schema (e.g., Customer, Product).

This question belongs to: Computer Database Management System (DBMS)

Question #2

What is the concept of referential integrity?

A. Ensuring data is normalized

B. Ensuring that no null values exist

C. Ensuring that all primary keys are unique

D. Ensuring that foreign key values match primary key values in the referenced table

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Correct Answer: Option D

Explanation:
Referential integrity ensures that relationships between tables remain consistent, meaning foreign key values must have corresponding primary key values.

This question belongs to: Computer Database Management System (DBMS)

Question #3

What is the purpose of the SQL 'JOIN' clause?

A. To delete records from a table

B. To combine columns from multiple tables into a single table

C. To combine rows from two or more tables based on a related column

D. To create a new table

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Correct Answer: Option C

Explanation:
JOIN is used to combine rows from different tables based on a common column, allowing querying across related tables.

This question belongs to: Computer Database Management System (DBMS)

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