Fourth Normal Form (4NF) in DBMS Theory - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Fourth Normal Form (4NF)

Which of the following best describes the main goal of Fourth Normal Form (4NF) in database design?

A To ensure that every non-key attribute is fully functionally dependent on the primary key.

B To remove all transitive dependencies so that non-key attributes depend only on the primary key.

C To eliminate multi-valued dependencies and ensure that no table contains two or more independent multi-valued facts about an entity.

D To organize data into tables to reduce redundancy by splitting data into smaller tables linked by foreign keys.

💡 Hint

Think about what kind of dependencies 4NF specifically targets beyond 3NF.

4NF focuses on removing multi-valued dependencies, which occur when a table contains two or more independent sets of multi-valued attributes. This prevents storing unrelated multiple facts in the same table.

📋 Factual

intermediate

Identifying Multi-Valued Dependencies

Which of the following is an example of a multi-valued dependency that violates Fourth Normal Form (4NF)?

A A table where a student can have multiple phone numbers and multiple email addresses, and these sets are independent of each other.

B A table where each employee has a unique ID and a single department they belong to.

C A table where each product has a unique code and a single price.

D A table where orders are linked to customers and each order has a single date.

💡 Hint

Look for a case where two sets of multiple values exist independently for the same entity.

When a student has multiple phone numbers and multiple email addresses independently, it creates multi-valued dependencies. This violates 4NF because these independent multi-valued facts should be stored in separate tables.

🔍 Analysis

advanced

Analyzing Table Structure for 4NF Violation

Consider a table storing information about books, authors, and genres. Each book can have multiple authors and multiple genres, and these sets are independent. What is the best way to normalize this table to satisfy Fourth Normal Form (4NF)?

A Split the table into three tables: one for books, one linking books to authors, and one linking books to genres.

B Keep the table as is but add a composite primary key combining book, author, and genre.

C Create a single table with columns for book, author, genre, and a unique ID for each row.

D Merge authors and genres into a single column separated by commas.

💡 Hint

Think about how to separate independent multi-valued facts into different tables.

Since authors and genres are independent multi-valued attributes of books, 4NF requires splitting them into separate tables to remove multi-valued dependencies.

❓ Comparison

advanced

Difference Between 3NF and 4NF

Which statement correctly distinguishes Fourth Normal Form (4NF) from Third Normal Form (3NF)?

A 3NF and 4NF both remove the same types of dependencies but in different orders.

B 3NF removes multi-valued dependencies, while 4NF removes transitive dependencies.

C 3NF focuses on key constraints, while 4NF focuses on foreign key constraints.

D 3NF removes transitive dependencies, while 4NF removes multi-valued dependencies.

💡 Hint

Recall what each normal form targets specifically.

3NF eliminates transitive dependencies where non-key attributes depend on other non-key attributes. 4NF goes further to remove multi-valued dependencies where multiple independent multi-valued attributes exist.

❓ Reasoning

expert

Impact of Ignoring 4NF in Database Design

What is a likely consequence of not applying Fourth Normal Form (4NF) when designing a database that contains multi-valued dependencies?

A The database will automatically prevent duplicate entries through primary keys.

B Data redundancy increases, leading to potential inconsistencies and larger storage requirements.

C Queries will always run faster because data is stored in fewer tables.

D Foreign key constraints will be ignored, causing referential integrity issues.

💡 Hint

Consider what happens when independent multi-valued data is stored together.

Ignoring 4NF causes multi-valued dependencies to remain, which leads to repeated data entries, increasing redundancy and the chance of inconsistent data.