What is Normalization in MySQL?

Simple Explanation :

Normalization in MySQL refers to the process of organizing and structuring a relational database to minimize redundancy and dependency. The goal of normalization is to ensure data integrity, reduce data duplication, and maintain a consistent and efficient database structure. This is achieved by breaking down a large table into smaller tables and defining relationships between them.

There are several normal forms in database normalization, each with specific rules and requirements. The most common normal forms are:


1. First Normal Form (1NF): Ensures that each column contains only atomic (indivisible) values, and there are no repeating groups or arrays within a column.

2. Second Normal Form (2NF): Builds upon 1NF and ensures that each non-key column is fully functionally dependent on the primary key, meaning that no partial dependencies exist.

3. Third Normal Form (3NF): Builds upon 2NF and eliminates transitive dependencies, meaning that non-key columns should not depend on other non-key columns.

4. Boyce-Codd Normal Form (BCNF): An extension of 3NF that addresses situations where there are non-trivial dependencies between candidate keys and other attributes.

Briefly Explanation :

1. First Normal Form (1NF): In the context of relational databases, a table is considered to be in the First Normal Form if it meets the following conditions:

All columns contain atomic (indivisible) values. This means that each cell in the table should hold a single, simple value, rather than a collection of values.
There are no repeating groups or arrays within a column. Each column should store a single value for each row.

For example, consider a table containing information about students and their courses:

Student ID	Name	Courses
1	John	Math, Physics
2	Jane	Chemistry

This table violates 1NF because the "Courses" column contains a list of courses. To bring it into 1NF, you could split the courses into separate rows for each student:

Student ID	Name	Course
1	John	Math
1	John	Physics
2	Jane	Chemistry

2. Second Normal Form (2NF): A table is in Second Normal Form if it satisfies 1NF and also meets the following condition:

Every non-key column is fully functionally dependent on the entire primary key. This means that there should be no partial dependencies, where non-key attributes depend on only a part of the primary key.

For example, let's consider a table that records sales information:

Order ID	Product ID	Product Name	Category
1	101	Laptop	Electronics
2	102	Phone	Electronics
3	101	Laptop	Electronics

Here, the combination of "Order ID" and "Product ID" forms the primary key. However, the "Product Name" and "Category" attributes are partially dependent on "Product ID" alone, violating 2NF. To achieve 2NF, you would separate the product information into a separate table, eliminating the partial dependency.

3. Third Normal Form (3NF): A table is in Third Normal Form if it satisfies 2NF and also meets the following condition:

There are no transitive dependencies, meaning that non-key columns should not depend on other non-key columns.

For example, consider a table that tracks information about teachers and the departments they are in:

Teacher ID	Teacher Name	Department	Department Head
1	Alice	Mathematics	Bob
2	Bob	Physics	NULL

Here, the "Department Head" attribute depends on the "Department" attribute, which is not part of the primary key. This is a transitive dependency and violates 3NF. To achieve 3NF, you would separate the department information into a separate table and eliminate the transitive dependency.

 A table is in BCNF if it satisfies 3NF and also meets the following condition:

For every non-trivial functional dependency X -> Y, X must be a superkey. In simpler terms, a non-key column should be fully functionally dependent on a candidate key.