First Normal Form (1NF) in DBMS

1. Introduction

Normalization is a systematic approach used in DBMS to organize data efficiently and reduce redundancy. The First Normal Form (1NF) is the first step in the normalization process.

It ensures that the table structure is simple, consistent, and free from repeating groups.

2. Definition of First Normal Form (1NF)

A relation (table) is said to be in First Normal Form (1NF) if:

• All attributes contain atomic (indivisible) values
• Each field contains only one value
• There are no repeating groups or multi-valued attributes
• Each record can be uniquely identified (using a primary key) 

3. Key Concepts in 1NF

3.1 Atomic Values

An attribute is atomic if it cannot be divided further.

• Valid: "Ajay"
• Invalid: "Ajay, Ravi" (multiple values in one field) 

3.2 No Repeating Groups

A table should not have multiple columns storing similar types of data.

• Invalid: Phone1, Phone2, Phone3
• Valid: Separate rows for each phone number 

3.3 Single-Valued Attributes

Each cell must contain only one value, not a list or set.

4. Example of Table NOT in 1NF

Student Table

Problems

• "Courses" contains multiple values
• Violates atomicity
• Difficult to query and update 

5. Converting to First Normal Form

To convert into 1NF, we eliminate multi-valued attributes by creating separate rows.

Converted Table (1NF)

6. Another Example (Repeating Groups)

Table NOT in 1NF

Problem

• Repeating group (Phone1, Phone2)
• Not scalable (what if more numbers?) 

Converted to 1NF

7. Steps to Achieve 1NF

1. Identify multi-valued attributes
2. Remove repeating groups
3. Ensure each column contains atomic values
4. Create separate rows for multiple values
5. Define a primary key 

8. Advantages of 1NF

• Eliminates data redundancy (partially)
• Improves data consistency
• Simplifies querying
• Prepares database for higher normal forms 

9. Limitations of 1NF

• Does not remove all redundancy
• Does not handle functional dependencies
• Still may have update, insertion, deletion anomalies