SQL MCQs – Database Design and Normalization

Database design and normalization are fundamental to creating efficient and scalable databases. Good design ensures that data is stored logically and reduces redundancy. Normalization organizes data into tables and minimizes dependency issues by dividing larger tables into smaller, related ones. Concepts like primary keys, foreign keys, functional dependencies, and normal forms (1NF, 2NF, 3NF, BCNF) are vital. Preparing for these topics with multiple-choice questions (MCQs) enhances your knowledge and ensures confidence during interviews.

1.) What does ER stand for in ER Diagram?

A) Entity Relationship
B) Entity Reference
C) Event Reaction
D) External Resource

Answer: Option A

Explanation: ER diagrams model the relationships between entities in a database.

2.) What is the key benefit of schema normalization in large databases?

A) Simplifies data visualization
B) Reduces storage requirements and improves data consistency
C) Eliminates indexing needs
D) Ensures better data visualization

Answer: Option B

Explanation: Schema normalization reduces redundancy, saving storage and ensuring data consistency in large databases.

3.) What does a foreign key represent in a database?

A) A unique identifier for each record
B) A key that cannot be used
C) A default value for columns
D) A reference to a primary key in another table

Answer: Option D

Explanation: A foreign key establishes relationships between tables.

4.) What is the purpose of indexing in SQL?

A) To reduce redundancy
B) To speed up queries
C) To increase redundancy
D) To normalize tables

Answer: Option B

Explanation: Indexes improve query performance by reducing search time.

5.) What is the first step in database normalization?

A) Eliminating redundant data
B) Removing foreign keys
C) Ensuring all columns are atomic
D) Adding composite keys

Answer: Option C

Explanation: In 1NF, all columns must contain atomic (indivisible) values.

6.) Which normal form eliminates partial dependency?

A) 1NF
B) 2NF
C) 3NF
D) BCNF

Answer: Option B

Explanation: 2NF removes partial dependency on a composite primary key.

7.) Which normal form eliminates transitive dependency?

A) 1NF
B) 2NF
C) 3NF
D) 4NF

Answer: Option C

Explanation: 3NF ensures non-prime attributes are only dependent on primary keys.

8.) What does BCNF stand for?

A) Boyce-Codd Normal Form
B) Binary Conjugate Normal Form
C) Basic Composite Normal Form
D) None of the above

Answer: Option A

Explanation: BCNF is a stricter version of 3NF.

9.) What is functional dependency in a database?

A) A relationship between two tables
B) A dependency between primary keys
C) A function that manages data
D) A relationship between two columns

Answer: Option D

Explanation: Functional dependency occurs when one column’s value depends on another’s.

10.) What happens if a table is not normalized?

A) Improved performance
B) Increased redundancy and anomalies
C) Reduced storage usage
D) Elimination of relationships

Answer: Option B

Explanation: Lack of normalization leads to redundant data and inconsistencies.

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