Database Normalizer

Interactive guide to database normalization forms (1NF through 5NF/BCNF). Learn with visual examples showing denormalized data and properly normalized results.

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Database Normalizer

Interactive guide to database normalization forms (1NF through 5NF/BCNF). Learn with visual examples showing denormalized data and properly normalized results.

🔒All processing happens in your browser. No data is uploaded.

Normalization Forms Overview

1NF

2NF

3NF

BCNF

4NF

5NF

1NF

2NF

3NF

BCNF

4NF

5NF

1NF

Rule: Each column must contain only atomic (indivisible) values. No repeating groups or arrays.

First Normal Form eliminates repeating groups by ensuring each cell contains a single value. Tables should have a primary key and no multi-valued attributes.

Violation Example & Fix

The Courses column contains multiple comma-separated values, violating the atomicity requirement of 1NF.

Before (Denormalized)

StudentID	Name	Courses
1	Alice	Math, Physics, Chemistry
2	Bob	English, Math
3	Carol	Biology, Chemistry, Physics

After (Normalized)

StudentCourses

StudentID	Name	Course
1	Alice	Math
1	Alice	Physics
1	Alice	Chemistry
2	Bob	English
2	Bob	Math
3	Carol	Biology
3	Carol	Chemistry
3	Carol	Physics

SQL Examples

SQL Before (Violates Normal Form)

-- Violates 1NF: multi-valued column
CREATE TABLE Students (
  StudentID INT PRIMARY KEY,
  Name VARCHAR(100),
  Courses VARCHAR(500)  -- comma-separated!
);

SQL After (Normalized)

-- 1NF: Each cell has atomic values
CREATE TABLE Students (
  StudentID INT PRIMARY KEY,
  Name VARCHAR(100)
);

CREATE TABLE StudentCourses (
  StudentID INT,
  Course VARCHAR(100),
  PRIMARY KEY (StudentID, Course),
  FOREIGN KEY (StudentID) REFERENCES Students(StudentID)
);