DBMS 4NF

Introduction

A database management system (DBMS) is a software application that enables users to define, create, maintain and control access to a database. Normalization is the process of organizing data in a database to minimize redundancy. Fourth normal form (4NF) is the highest level of normalization that is typically used.

What is 4NF?

Fourth normal form (4NF) is a level of database normalization where no non-prime attribute is dependent on any other non-prime attribute. In other words, there should be no dependencies between non-key attributes.

Why is 4NF important?

The higher the level of normalization, the less redundancy there is in the database. This means that data is stored only once, which reduces the risk of errors, inconsistencies and redundancies. Therefore, 4NF is important for ensuring data accuracy, consistency and integrity.

How to achieve 4NF?

To achieve 4NF, follow these steps:

1. Start with a normalized database that is in third normal form (3NF).
2. Identify all functional dependencies between non-key attributes.
3. Decompose the table(s) into smaller tables using the identified functional dependencies.
4. Verify that all tables are in 4NF.

Example

Assume we have a table of orders with the following attributes: order_id, customer_id, product_id, product_name, product_description, price.

To achieve 4NF, we first identify the functional dependencies:

• order_id -> customer_id
• product_id -> product_name, product_description, price

Then, we decompose the table into three smaller tables:

Table 1: orders(order_id, customer_id)

Table 2: products(product_id, product_name, product_description)

Table 3: order_details(order_id, product_id, price)

By doing this, we have eliminated the redundancy in the original table and have achieved 4NF.

Conclusion

DBMS 4NF is a high level of database normalization that eliminates the redundancy in a database. It ensures data accuracy, consistency and integrity. Achieving 4NF requires starting with a normalized database that is in third normal form (3NF), identifying functional dependencies, decomposing the table(s) into smaller tables, and verifying that all tables are in 4NF.