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
Two-Dimensional Structure
Each table has rows and columns.
Each row represents one entity instance.
Each column represents one attribute.
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.
No Repeating Groups
A row cannot have repeated columns like
Course1,Course2,Course3.Instead, each course should be stored in a separate row.
Example of a Non-1NF Table
| Roll_No | Name | Courses |
|---|---|---|
| 101 | Aman | DBMS, OS |
| 102 | Riya | DBMS, CN, SE |
Here, Courses is a non-atomic column with multiple values.
Converting to 1NF
To bring a table into 1NF:
Split non-atomic columns so each cell has one value.
Move repeating attributes into separate rows using a key.
Using the STUDENT example:
Original with Non-Atomic Column
STUDENT(Roll_No, Name, Courses)
where Courses holds multiple subjects.
After 1NF (Split Rows)
| Roll_No | Name | Course |
|---|---|---|
| 101 | Aman | DBMS |
| 101 | Aman | OS |
| 102 | Riya | DBMS |
| 102 | Riya | CN |
| 102 | Riya | SE |
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.