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Normalization

Database normalization is a technique to reduce redundancy and dependency in database schemas by splitting large tables into smaller ones and defining relationships. It follows a set of rules known as normal forms, including First Normal Form (1NF), Second Normal Form (2NF), Third Normal Form (3NF), Boyce-Codd Normal Form (BCNF), Fourth Normal Form (4NF), and Fifth Normal Form (5NF). The process enhances clarity in data organization and is essential for effective database design.

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19 views4 pages

Normalization

Database normalization is a technique to reduce redundancy and dependency in database schemas by splitting large tables into smaller ones and defining relationships. It follows a set of rules known as normal forms, including First Normal Form (1NF), Second Normal Form (2NF), Third Normal Form (3NF), Boyce-Codd Normal Form (BCNF), Fourth Normal Form (4NF), and Fifth Normal Form (5NF). The process enhances clarity in data organization and is essential for effective database design.

Uploaded by

Suresh
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Database normalization is a database schema design technique, by which an

existing schema is modified to minimize redundancy and dependency of data.


Normalization split a large table into smaller tables and define relationships between
them to increases the clarity in organizing data.
Table of Contents

Some Facts About Database Normalization

 The words normalization and normal form refer to the structure of a database.
 Normalization was developed by IBM researcher E.F. Codd In the 1970s.
 Normalization increases clarity in organizing data in Databases.
Normalization of a Database is achieved by following a set of rules called 'forms' in
creating the database.

Database Normalization Rules


The database normalization process is divided into following the normal form:

 First Normal Form (1NF)


 Second Normal Form (2NF)
 Third Normal Form (3NF)
 Boyce-Codd Normal Form (BCNF)
 Fourth Normal Form (4NF)
 Fifth Normal Form (5NF)

First Normal Form (1NF)


Each column is unique in 1NF.
Example:
Sample Employee table, it displays employees are working with multiple
departments.
Employee Age Department

Melvin 32 Marketing, Sales

Edward 45 Quality Assurance

Alex 36 Human Resource

Employee table following 1NF:


Employee Age Department

Melvin 32 Marketing

Melvin 32 Sales
Edward 45 Quality Assurance

Alex 36 Human Resource

Second Normal Form (2NF)


The entity should be considered already in 1NF, and all attributes within the entity
should depend solely on the unique identifier of the entity.
Example:
Sample Products table:

Create table product (productId int, Product varchra(20), branch varchar(20),


constraint pk1 primary key (productid,product));

Select prodct, qty,price from product where id<100;


..

...
.

Create view productview as prodct, qty,price from product where id<100;


Select *... from productview;

productID product Brand

1 Monitor Apple

2 Monitor Samsung

3 Scanner HP

4 Head phone JBL

Product table following 2NF:


Products Category table:
productID product

1 Monitor

2 Scanner
3 Head phone

Brand table:
brandI brand
D

1 Apple

2 Samsung

3 HP

4 JBL

Products Brand table:


pbID productID brandID

1 1 1

2 1 2

3 2 3

4 3 4

Third Normal Form (3NF)


The entity should be considered already in 2NF, and no column entry should be
dependent on any other entry (value) other than the key for the table.
If such an entity exists, move it outside into a new table.
3NF is achieved, considered as the database is normalized.

Boyce-Codd Normal Form (BCNF)


3NF and all tables in the database should be only one primary key.

Fourth Normal Form (4NF)


Tables cannot have multi-valued dependencies on a Primary Key.

Fifth Normal Form (5NF)


A composite key shouldn't have any cyclic dependencies.
Well, this is a highly simplified explanation for Database Normalization. One can
study this process extensively, though. After working with databases for some time,
you'll automatically create Normalized databases, as it's logical and practical.

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