Database Normalization

In databases, 1N, 2N, 3N refer to 1NF, 2NF, 3NF — the first three normal forms in database normalization. These are rules to organize relational data efficiently and eliminate redundancy.

✅ 1NF (First Normal Form)

📌 Rule:

• Each column should have atomic (indivisible) values.
• No repeating groups or arrays in a single column.

❌ Bad Example:

ID	Name	Phone Numbers
1	Aftab	12345, 67890

✅ Good Example (1NF applied):

ID	Name	Phone
1	Aftab	12345
1	Aftab	67890

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✅ 2NF (Second Normal Form)

📌 Rule:

1. Be in 1NF
2. Remove partial dependencies (i.e., non-key columns should depend on the whole primary key)

❌ Bad Example (composite key: OrderID, ProductID):

OrderID	ProductID	ProductName	CustomerName
1	101	Mouse	Aftab

 

➡️ CustomerName depends only on OrderID, not the full composite key.

✅ Fix:

Split into:

1. Order table (OrderID, CustomerName)
2. OrderDetails table (OrderID, ProductID, ProductName)

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✅ 3NF (Third Normal Form)

📌 Rule:

• Be in 2NF
• No transitive dependencies (i.e., non-key columns shouldn’t depend on other non-key columns)

❌ Bad Example:

StudentID	Name	Department	HOD
1	Raj	IT	Dr. Mehta

 

➡️ HOD depends on Department, not directly on StudentID.

✅ Fix:

Split into:

• Student table (StudentID, Name, Department)
• Department table (Department, HOD)

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🧠 Summary Table: