In relational database design, 1NF (First Normal Form) is the first step of normalization. A table is in 1NF if it satisfies three basic rules:

  • The table is two‑dimensional with rows and columns.

  • All column values are atomic (indivisible).

  • There are no repeating groups in a single row.

1NF removes the most obvious structural problems from a table and prepares it for higher normal forms.

Rules of 1NF

1. Two‑Dimensional Structure

  • Each table has rows and columns.

  • Each row represents one entity instance.

  • Each column represents one attribute.

2. Atomic Values

  • Each cell must contain a single, indivisible value.

  • Values like lists, sets, or multiple numbers in one cell are not allowed.

For example, a cell containing C101,C102 is not atomic and must be split.

3. No Repeating Groups

  • A row cannot have repeated columns like Course1, Course2, Course3.

  • Instead, each course should be in a separate row.

Example of a non‑1NF table:

Roll_NoNameCourses
101AmanDBMS, OS
102RiyaDBMS, CN, SE

Here, Courses is a non‑atomic column with multiple values.

Converting to 1NF

To bring a table into 1NF:

  1. Split non‑atomic columns so each cell has one value.

  2. Move repeating attributes into separate rows using a key.

Using the STUDENT example:

  • Original with non‑atomic column:

    • STUDENT(Roll_No, Name, Courses) with Courses holding multiple subjects.

  • After 1NF (split rows):

Roll_NoNameCourse
101AmanDBMS
101AmanOS
102RiyaDBMS
102RiyaCN
102RiyaSE

Now:

  • Each cell is atomic.

  • There are no repeating groups.

  • The table is in 1NF.

Why 1NF Matters?

  • It is the minimum requirement for a relational table.

  • It eliminates messy, nested values and prepares the design for 2NF and 3NF.

  • It makes queries and indexing more predictable and easier to implement.

Summary

1NF in DBMS means that a table has atomic values in each cell, no repeating groups, and a clean two‑dimensional structure. To achieve 1NF, non‑atomic columns and repeating groups are split into multiple rows, ensuring that each piece of data is stored as a single, simple value. 1NF is the first step toward a well‑normalized relational database.