Fourth Normal Form (4NF) in DBMS Theory - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the main requirement of Fourth Normal Form (4NF).

DBMS Theory

A relation is in 4NF if it is in Boyce-Codd Normal Form and has no [1] dependencies.

Drag options to blanks, or click blank then click option'

Atransitive

Bfunctional

Cmultivalued

Dpartial

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing multivalued dependencies with functional dependencies.

Thinking 4NF only requires BCNF.

4NF requires that there are no multivalued dependencies other than a candidate key.

2fill in blank

medium

Complete the code to describe the condition for a relation to be in 4NF.

DBMS Theory

If a relation has a multivalued dependency X ->-> Y, then X must be a [1] key for the relation.

Drag options to blanks, or click blank then click option'

Acandidate

Bsuper

Cforeign

Dprimary

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing primary key instead of candidate key.

Confusing foreign key with candidate key.

In 4NF, for any multivalued dependency X ->-> Y, X must be a candidate key.

3fill in blank

hard

Fix the error in the statement about 4NF.

DBMS Theory

4NF eliminates [1] dependencies that are not functional dependencies.

Drag options to blanks, or click blank then click option'

Ajoin

Btransitive

Cpartial

Dmultivalued

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing multivalued dependencies with transitive dependencies.

Thinking 4NF deals with join dependencies.

4NF eliminates multivalued dependencies that are not functional dependencies.

4fill in blank

hard

Fill both blanks to complete the definition of 4NF.

DBMS Theory

A relation is in 4NF if it is in [1] and has no [2] dependencies except those involving a candidate key.

Drag options to blanks, or click blank then click option'

ABCNF

B3NF

Cmultivalued

Dfunctional

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 3NF instead of BCNF.

Confusing functional dependencies with multivalued dependencies.

4NF requires the relation to be in BCNF and have no multivalued dependencies except those involving a candidate key.

5fill in blank

hard

Fill all three blanks to complete the example of 4NF violation and its resolution.

DBMS Theory

If a relation has attributes A, B, and C, and there are multivalued dependencies [1] and [2], then to achieve 4NF, decompose into relations with keys [3].

Drag options to blanks, or click blank then click option'

AA ->-> B

BA ->-> C

CA

DB

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up which attributes are keys.

Not decomposing the relation to remove multivalued dependencies.

When a relation has multivalued dependencies A ->-> B and A ->-> C, it violates 4NF. Decomposing into relations with key A removes the violation.

Practice

1. What is the main purpose of Fourth Normal Form (4NF) in database design?

easy

A. To organize data into tables with fewer columns

B. To ensure every attribute depends on the primary key

C. To eliminate transitive dependencies

D. To remove multi-valued dependencies and avoid repeated data combinations

Solution

1. Step 1: Understand the role of 4NF

   4NF focuses on removing multi-valued dependencies, which cause repeated combinations of independent data.

2. Step 2: Compare with other normal forms

   Other normal forms like 2NF and 3NF handle partial and transitive dependencies, but 4NF specifically targets multi-valued dependencies.

3. Final Answer:

   To remove multi-valued dependencies and avoid repeated data combinations -> Option D

4. Quick Check:

   4NF = Remove multi-valued dependencies [OK]

Hint: 4NF removes repeated independent data pairs [OK]

Common Mistakes:

• Confusing 4NF with 3NF or BCNF
• Thinking 4NF only deals with primary keys
• Ignoring multi-valued dependencies

2. Which of the following conditions must a table satisfy before it can be in Fourth Normal Form (4NF)?

easy

A. It must be in Boyce-Codd Normal Form (BCNF)

B. It must have only one candidate key

C. It must have no foreign keys

D. It must be in First Normal Form (1NF)

Solution

1. Step 1: Recall 4NF prerequisites

   4NF requires the table to be in BCNF first to ensure no anomalies from functional dependencies.

2. Step 2: Eliminate incorrect options

   1NF is a lower normal form; having no foreign keys or only one candidate key is not a requirement for 4NF.

3. Final Answer:

   It must be in Boyce-Codd Normal Form (BCNF) -> Option A

4. Quick Check:

   4NF requires BCNF first [OK]

Hint: 4NF needs BCNF before multi-valued fixes [OK]

Common Mistakes:

• Assuming 1NF is enough for 4NF
• Confusing foreign keys with normalization rules
• Believing 4NF limits candidate keys

3. Consider a table with columns StudentID, Course, and Hobby. Each student can enroll in multiple courses and have multiple hobbies independently. Which problem does this table violate if not in 4NF?

medium

A. Multi-valued dependency

B. Transitive dependency

C. Partial dependency

D. Functional dependency

Solution

1. Step 1: Identify dependencies in the table

   StudentID relates independently to multiple Courses and multiple Hobbies, causing multi-valued dependencies.

2. Step 2: Understand 4NF violation

   Multi-valued dependencies cause repeated combinations of courses and hobbies, violating 4NF.

3. Final Answer:

   Multi-valued dependency -> Option A

4. Quick Check:

   Independent multiple values = Multi-valued dependency [OK]

Hint: Multiple independent lists cause multi-valued dependency [OK]

Common Mistakes:

• Confusing multi-valued with functional dependency
• Thinking partial or transitive dependencies apply here
• Ignoring independent multi-values

4. Given a table with columns EmployeeID, Project, and Skill, where each employee can work on multiple projects and have multiple skills independently, what is the best way to fix a 4NF violation?

medium

A. Add more columns to combine projects and skills

B. Split the table into two tables: one for projects and one for skills

C. Remove the primary key

D. Create a composite key with all three columns

Solution

1. Step 1: Identify the multi-valued dependencies

   EmployeeID relates independently to multiple Projects and multiple Skills, causing multi-valued dependencies.

2. Step 2: Apply 4NF solution

   Splitting the table into two separate tables removes multi-valued dependencies by isolating independent facts.

3. Final Answer:

   Split the table into two tables: one for projects and one for skills -> Option B

4. Quick Check:

   Split tables to fix multi-valued dependencies [OK]

Hint: Split independent multi-values into separate tables [OK]

Common Mistakes:

• Adding columns increases complexity
• Removing primary key breaks uniqueness
• Using composite keys doesn't remove multi-valued dependencies

5. A database table stores AuthorID, BookTitle, and Genre. Each author can write multiple books and write in multiple genres independently. How should the table be redesigned to satisfy Fourth Normal Form (4NF)?

hard

A. Keep the table as is and add a composite primary key

B. Add a new column combining book and genre into one field

C. Create two tables: one linking authors to books, another linking authors to genres

D. Remove the genre column entirely

Solution

1. Step 1: Identify multi-valued dependencies

   AuthorID relates independently to multiple BookTitles and multiple Genres, causing multi-valued dependencies.

2. Step 2: Redesign to remove multi-valued dependencies

   Splitting into two tables--one for author-book and one for author-genre--removes repeated combinations and satisfies 4NF.

3. Final Answer:

   Create two tables: one linking authors to books, another linking authors to genres -> Option C

4. Quick Check:

   Separate independent multi-values into tables [OK]

Hint: Split independent lists into separate tables for 4NF [OK]

Common Mistakes:

• Combining fields creates complex data
• Removing columns loses important info
• Assuming composite keys fix multi-valued dependencies