Database develop. life cycle - First Normal Form (1NF)

First Normal Form (1NF)

1. Definition

A table is in First Normal Form (1NF) if:

  1. All attributes contain atomic (indivisible) values.

  2. Each column has values of the same data type.

  3. There are no repeating groups or arrays in a single column.

In simple words: No multiple values in one cell, and no repeating columns for the same type of data.

2. Example – Before 1NF

Consider a Student table:

StudentID Name Phone Numbers Courses
101 Alice 555-1234, 555-5678 DBMS, Networks
102 Bob 555-8765 DBMS

Problems:

  • Phone Numbers column has multiple values (not atomic).

  • Courses column also has multiple values.

This table violates 1NF.

3. Transforming to 1NF

We must:

  • Ensure atomic values.

  • Eliminate repeating groups by creating separate rows.

Student Table in 1NF:

StudentID Name Phone Course
101 Alice 555-1234 DBMS
101 Alice 555-5678 Networks
102 Bob 555-8765 DBMS

Now:

  • Each cell contains a single value.

  • No repeating groups.

  • Data is structured properly.

4. Key Notes

  • Sometimes converting to 1NF increases the number of rows.

  • 1NF is the foundation of normalization — higher forms (2NF, 3NF, etc.) build on it.

5. Why It Matters

  • Removes ambiguity in storing and retrieving data.

  • Makes queries (like finding all students enrolled in “DBMS”) more straightforward.

  • Prevents update, insertion, and deletion anomalies.