Rules of Database Normalization

Rules of DatabaseNormalization

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What is Normalization? What is the objective of Normalization? Why is Normalization in a database

important? What are NORMAL FORMS? How do we accomplish Normalization in our

database? Are there times when Normalization is

unnecessary?

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Overview

Normalization refers to the process of creating an efficient, reliable, flexible, and appropriate “relational” structure for storing information in a “relational” data structure.

Normalization usually involves dividing a database into two or more tables and defining the relationship between the tables.

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What is Normalization?

The objective is to isolate data so that additions, deletions, and modifications of a field can be made in just one table and then propagated through the rest of the database via the defined relationships.

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What is the objective of Normalization?

Normalization removes redundant data from your tables in order to improve storage efficiency.

Normalization removes redundant data and improves data integrity.

Normalization removes redundant data and helps in maintenance problems. Example: If data that exists in more than one place must be changed, the data must be changed in exactly the same way in all locations.

Finally, Normalization removes redundant data and improves the scalability of your database.

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Why is Normalization in a database important?

A series of logical steps to normalize data tables. First Normal Form-1NF Second Normal Form-2NF Third Normal Form-3NF Fourth Normal Form-4NF Fifth Normal Form-5NF• We will learn the First, Second and Third

Normal Forms

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What are NORMAL FORMS?

The definition of the first Normal Form is as follows

There are no repeating groups.All of the key attributes are defined.All attributes are dependent on the primary

key.Example on the next slide.

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What is the First Normal Form?

How do we accomplish First Normal Form? Look at this example.

ProjectNumber

ProjectName

EmployeeNumber

EmployeeName-1

Rate Category-1

Hourly Rate-1

EmployeeName 2

Rate Category

Hourly Rate

1023, 1056

MadagascarTravel site andOnlineEstate Agency

11 Julius Wilson A $60 Monica Jefferson

B $50

1023 MadagascarTravel site

16 Daniel Moore C $40

1056 Online Estate Agency

17 Charles Saul D $30

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Notice the repeating Groups.

ProjectNumber

ProjectName

EmployeeNumber

EmployeeName-1

Rate Category-1

Hourly Rate-1

EmployeeName 2

Rate Category

Hourly Rate

1023, 1056

MadagascarTravel site andOnlineEstate Agency

11 Julius Wilson A $60 Monica Jefferson

B $50



1056Online Estate Agency


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This is our solution to eliminating the repeating groups

ProjectNumber

ProjectName

EmployeeNumber

EmployeeName

Rate Category

Hourly Rate


11 Julius Wilson A $60


12 Monica Jefferson

B $50







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How can we set our Primary Key?

ProjectNumber

ProjectName

EmployeeNumber

EmployeeName

Rate Category

Hourly Rate




12 Monica Jefferson

B $50







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Can this be our Primary Key?

ProjectNumber

ProjectName

EmployeeNumber

EmployeeName

Rate Category

Hourly Rate




12 Monica Jefferson

B $50







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Or, can this be our Primary Key?

ProjectNumber

ProjectName

EmployeeNumber

EmployeeName

Rate Category

Hourly Rate




12 Monica Jefferson

B $50







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Solution-We need both as our Primary Keys.

ProjectNumberPrimary Key

ProjectName

EmployeeNumberPrimary Key

EmployeeName

Rate Category

Hourly Rate




12 Monica Jefferson

B $50







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Is our table in First Normal Form?


ProjectName


EmployeeName

Rate Category

Hourly Rate




12 Monica Jefferson

B $50







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A table is in 2nd Normal Form if:1) It is in 1st normal form.2) It includes no partial dependencies (where

an attribute is dependent on only a part of a primary key).

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What is Second Normal Form

Does it include partial dependencies? Do you notice anything else?


ProjectName


EmployeeName

Rate Category

Hourly Rate




12 Monica Jefferson

B $50

1023 MadagascatTravel site






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Look at “Project Name” Row 3. Also look at Hourly Rate? What about

data integrity?ProjectNumberPrimary Key

ProjectName


EmployeeName

Rate Category

Hourly Rate




12 Monica Jefferson

B $50

1023 MadagascatTravel site






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Step One:ProjectName

EmployeeNumber

1023 11

1023 12

1023 16

1056 11

1056 17

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Project Name is only Dependent on Project Number; so, we create a“Employee Project Table.”

Employee-Project Table

Step Two:


ProjectName



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Notice that “Project Name” is dependent on only“Project Number.”We create our “Project Table” With Project Number as our Primary Key. Look at the space we have saved. What else have we done?

Project Table

Step Three:


EmployeeName

Rate Category

Hourly Rate


12 Monica Jefferson

B $50



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Notice that Employee Name, Rate Category, and Hourly Rate are dependent onEmployee Number.We create our “Employee Table” withEmployee Number as our Primary Key.

Employee Table

Are we now in Second Normal Form?

ProjectNamePrimary Key

EmployeeNumber Primary Key

1023 11

1023 12

1023 16

1056 11

1056 17

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Project Table Employee TableEmployee Project Table

Is it in First Normal Form and does it includes no partial Dependencies?


ProjectName




EmployeeName

Rate Category

Hourly Rate


12 Monica Jefferson B $50



Project Table



1023 11

1023 12

1023 16

1056 11

1056 17

Employee Project Table

It is in SECOND Normal Form. It contains no transitive dependencies

(where a non-key attribute is dependent on another non-key attribute).

Let’s see where we begin.

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Now, What is Third Normal Form?

Let’s take another look at what we have.?



1023 11

1023 12

1023 16

1056 11

1056 17

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Project Table Employee TableEmployee Project Table


ProjectName




EmployeeName

Rate Category

Hourly Rate





Project TableEmployee Project Table

Can we do anything else with this table?

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Let’s look at the Employee Project Table



1023 11

1023 12

1023 16

1056 11

1056 17

Employee Project Table

Let’s Look at the Project Table.


ProjectName


1056

Online Estate Agency

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Can we do anything else with this table?

Project Table

Can we further normalize this table?

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Let’s look at the Employee table

Employee Table


EmployeeName

Rate Category

Hourly Rate





See what we can do with the employee table.

Let’s make an “Rate” Table

Rate CategoryPrimary Key

Hourly Rate

A $60

B $50

C $40

D $30

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Employee Table


EmployeeName

Rate Category

11 Julius Wilson A

12 Monica Jefferson B

16 Daniel Moore C

17 Charles Saul D

Rate Table

We have now reduced the possibility of Employees being paidIncorrectly. Our database Will have more integrity.

That’s It!

Our data is now in 3NF.. Ready to be used in a DBMS…

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Documents

Rules of Database Normalization