BCNF and Higher Normal Forms

Introduction

Database normalization is essential for reducing redundancy and improving data integrity. BCNF (Boyce-Codd Normal Form) and higher normal forms are advanced stages of the normalization process.

BCNF (Boyce-Codd Normal Form)

BCNF is a stricter version of the Third Normal Form (3NF). A table is in BCNF if:

• It is in 3NF.
• Every determinant is a candidate key.

Example of BCNF

CREATE TABLE Courses (
    CourseID INT PRIMARY KEY,
    InstructorID INT,
    InstructorName VARCHAR(255),
    FOREIGN KEY (InstructorID) REFERENCES Instructors(InstructorID)
);

In this example, if an instructor teaches multiple courses, we may have multiple rows with the same instructor name. This violates BCNF since InstructorName is not a candidate key.

Higher Normal Forms

Higher normal forms include Fourth Normal Form (4NF) and Fifth Normal Form (5NF). They address multi-valued dependencies and join dependencies, respectively.

Fourth Normal Form (4NF)

A table is in 4NF if:

• It is in BCNF.
• It has no multi-valued dependencies.

Fifth Normal Form (5NF)

A table is in 5NF if:

• It is in 4NF.
• It cannot be decomposed without losing information.

Best Practices

To achieve and maintain BCNF and higher normal forms, consider the following best practices:

1. Identify all functional dependencies.
2. Ensure every determinant is a candidate key.
3. Decompose tables to eliminate redundancy.
4. Continuously review and refine schema as requirements change.

FAQ