⚖️ Normalization

What is normalization in relational databases?


Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity.

What are different normal forms (1NF, 2NF, 3NF, BCNF)?

Normal Form	Rule	Example
1NF	No repeating groups or arrays; each cell contains atomic (indivisible) values.	A table with multiple phone numbers in one column should be split into rows.
2NF	1NF + no partial dependency on part of a composite key.	Order details table with product info split into separate product table.
3NF	2NF + no transitive dependency (non-key columns depending on other non-key columns).	Customer city stored separately in `City` table instead of `Customer`.
BCNF	Stronger form of 3NF where every determinant is a candidate key.	Rare cases of overlapping candidate keys.

Why is normalization important?


Normalization is important because it helps prevent data redundancy, reduces data duplication, and ensures data consistency. It also makes it easier to maintain and update the database.

Provide examples of normalized vs non-normalized tables.

Example:


-- Non-normalized table
CREATE TABLE Orders (
  id INT PRIMARY KEY,
  customer_id INT,
  order_date DATE,
  product_name VARCHAR(100),
  quantity INT,
  price DECIMAL(10, 2)
);
 
-- Normalized tables
CREATE TABLE Customers (
  id INT PRIMARY KEY,
  name VARCHAR(100),
  email VARCHAR(100)
);
 
CREATE TABLE Orders (
  id INT PRIMARY KEY,
  customer_id INT,
  order_date DATE,
  product_name VARCHAR(100),
  quantity INT,
  price DECIMAL(10, 2)
);