Why Normalize?
Normalization is the process of organizing a database to reduce redundancy and improve data integrity. Without normalization, you end up with duplicate data, update anomalies, and wasted storage.
The Problems Without Normalization
UNNORMALIZED: StudentCourses Table
┌────┬─────────┬─────────────────────────┐
│ ID │ Name │ Courses │
├────┼─────────┼─────────────────────────┤
│ 1 │ Alice │ Databases, Networking │
│ 2 │ Bob │ Databases, OS │
└────┴─────────┴─────────────────────────┘
Problems:
✗ Redundancy: "Alice" and "Databases" stored multiple times
✗ Update anomaly: If Alice changes name, must update multiple rows
✗ Insert anomaly: Can't add a course without a student
✗ Delete anomaly: Deleting Bob might lose course information
Normalization Process
NORMALIZED:
Students Enrollments Courses
┌────┬─────────┐ ┌────┬─────────┐ ┌────┬────────────┐
│ ID │ Name │ │SID │CrsID │ │ ID │ Title │
├────┼─────────┤ ├────┼─────────┤ ├────┼────────────┤
│ 1 │ Alice │ │ 1 │ 101 │ │101 │ Databases │
│ 2 │ Bob │ │ 1 │ 102 │ │102 │ Networking │
└────┴─────────┘ │ 2 │ 101 │ │103 │ OS │
│ 2 │ 103 │ └────┴────────────┘
└────┴─────────┘
✓ No redundancy
✓ Update name? One place to change
✓ Add course without student? Yes
✓ Delete student? Course data preserved