What is a primary key in a database table? MCQ with Answer and Explanation

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What is a primary key in a database table?

A. A key that uniquely identifies each row in a table

B. A key that references a column in another table

C. A key that can contain duplicate values

D. A key that is always numeric

Answer: Option A

Solution (By JKSSB Mock Tests)

A primary key is a column or set of columns that uniquely identifies each row in a table, ensuring entity integrity.

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

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Practice More Database Management System (DBMS) Questions

Question #1

What happens when a database transaction triggers a 'COMMIT' statement?

A. All changes made by the transaction are made permanent on disk storage.

B. The transaction pauses temporarily.

C. The database structure is dropped.

D. The transaction is aborted and wiped.

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Correct Answer: Option A

Explanation:
Executing a COMMIT statement instructs the database engine to save all data updates performed during the transaction permanently into physical storage.

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

Question #2

What is the term for a column in a database table?

A. Tuple

B. Relation

C. Entity

D. Attribute

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Correct Answer: Option D

Explanation:
An attribute is a column or field in a table, representing a property of the entity.

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

Question #3

The intentional process of introducing redundant data into a normalized database structure to optimize read query performance is called what?

A. Fragmentation

B. Decomposition

C. Denormalization

D. Normalization

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Correct Answer: Option C

Explanation:
Denormalization is a strategy applied to normalized databases where redundant data is selectively added to speed up complex read queries by minimizing costly table joins.

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

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