How Normalization Works in SQL & Types?

What does Normalization entail in SQL and what are its categories?
Normalization in SQL refers to the method of structuring a database to diminish redundancy and dependency, a crucial practice in database design for enhancing performance, security, and integrity.

The types of normalization include:

First Normal Form (1NF):
This fundamental level necessitates a table to have a unique primary key and avoid repeating groups. For instance, a table "Employees" with columns such as EmployeeID (primary key), Name, Age, and PhoneNumbers is not in 1NF due to the repeating groups within the "PhoneNumbers" column. To achieve 1NF, a separate table "PhoneNumbers" could be created, linking EmployeeID (foreign key) and PhoneNumber, while the original table retains EmployeeID, Name, and Age fields.

Second Normal Form (2NF):
A table attains 2NF when it's in 1NF, and all non-key columns rely on the entire primary key. Following the earlier example, if the "PhoneNumber" column in the "PhoneNumbers" table depends only on the EmployeeID, another table like "PhoneNumberTypes" with PhoneNumberTypeID (primary key), PhoneNumberID (foreign key), and PhoneNumberType columns can be created. The "PhoneNumbers" table will then only comprise the PhoneNumberID and PhoneNumber columns.

Third Normal Form (3NF):
A table achieves 3NF when it's in 2NF, and all non-key columns solely depend on the primary key. Continuing from the previous scenario, if the "PhoneNumberType" column in the "PhoneNumberTypes" table depends on both PhoneNumberID and PhoneNumberTypeID, a separate "PhoneNumberTypeLookup" table can be created with PhoneNumberTypeID (primary key) and PhoneNumberTypeDescription columns.

While there exist higher forms of normalization beyond 3NF, their practical application is less frequent. It's crucial to understand that normalization involves a balance between database design complexity and performance. Occasionally, denormalizing a database (introducing redundancy) can enhance performance by minimizing the number of necessary joins to retrieve data. However, this approach increases storage and maintenance overhead.

Conclusion:
Normalization streamlines database organization, diminishing redundancy and dependency to boost performance, security, and integrity. The normalization levels - 1NF, 2NF, and 3NF - successively reduce redundancy and dependency. It's a trade-off between design complexity and database performance, where denormalization may improve performance but at the expense of increased storage and maintenance.