11stst, 2, 2ndnd, and 3, and 3rdrd Normal FormsNormal Forms

By By

Carlos AlvaradoCarlos Alvarado

San Jose State UniversitySan Jose State University

OverviewOverview

Today we’ll talk about:Today we’ll talk about: Database NormalizationDatabase Normalization

Data Anomalies Caused by:Data Anomalies Caused by: Update, Insertion, DeletionUpdate, Insertion, Deletion

Brief History/OverviewBrief History/Overview 11st st Normal FormNormal Form 22nd nd Normal FormNormal Form 33rdrd Normal Form Normal Form ConclusionConclusion

Database NormalizationDatabase Normalization

The main goal of Database The main goal of Database Normalization is to restructure the Normalization is to restructure the logical data model of a database to:logical data model of a database to:

Eliminate redundancyEliminate redundancy Organize data efficiently Organize data efficiently Reduce the potential for data Reduce the potential for data

anomalies.anomalies.

Data AnomaliesData Anomalies

Data anomalies are inconsistencies in the Data anomalies are inconsistencies in the data stored in a database as a result of an data stored in a database as a result of an operation such as update, insertion, and/or operation such as update, insertion, and/or deletion.deletion.

Such inconsistencies may arise when have a Such inconsistencies may arise when have a particular record stored in multiple locations particular record stored in multiple locations and not all of the copies are updated.and not all of the copies are updated.

We can prevent such anomalies by We can prevent such anomalies by implementing 7 different level of implementing 7 different level of normalization called Normal Forms (NF)normalization called Normal Forms (NF)

We’ll only look at the first three. We’ll only look at the first three.

Brief History/OverviewBrief History/Overview

Database Normalization was first proposed by Database Normalization was first proposed by Edgar F. Codd.Edgar F. Codd.

Codd defined the first three Normal Forms, which Codd defined the first three Normal Forms, which we’ll look into, of the 7 known Normal Forms.we’ll look into, of the 7 known Normal Forms.

In order to do normalization we must know what In order to do normalization we must know what the requirements are for each of the three Normal the requirements are for each of the three Normal Forms that we’ll go over.Forms that we’ll go over.

One of the key requirements to remember is that One of the key requirements to remember is that Normal Forms are progressive. That is, in order to Normal Forms are progressive. That is, in order to have 3have 3rdrd NF we must have 2 NF we must have 2ndnd NF and in order to NF and in order to have 2have 2ndnd NF we must have 1 NF we must have 1stst NF. NF.

11st st Normal FormNormal FormThe RequirementsThe Requirements

The requirements to satisfy the 1The requirements to satisfy the 1stst NF: NF: Each table has a primary key: minimal set Each table has a primary key: minimal set

of attributes which can uniquely identify a of attributes which can uniquely identify a recordrecord

The values in each column of a table are The values in each column of a table are atomic (No multi-value attributes allowed).atomic (No multi-value attributes allowed).

There are no repeating groups: two There are no repeating groups: two columns do not store similar information in columns do not store similar information in the same table.the same table.

11st st Normal FormNormal FormExampleExample

Un-normalized Students Un-normalized Students table:table:

Normalized Students table:Normalized Students table:

StudentStudent##

AdvIAdvIDD

AdvNamAdvNamee

AdvRooAdvRoomm

ClassClass11

ClassClass22

123123 123A123A JamesJames 555555 102-8102-8 104-9104-9

124124 123B123B SmithSmith 467467 209-0209-0 102-8102-8

StudentStudent##

AdvIAdvIDD

AdvNamAdvNamee

AdvRooAdvRoomm

ClassClass##

123123 123A123A JamesJames 555555 102-8102-8

123123 123A123A JamesJames 555555 104-9104-9

124124 123B123B SmithSmith 467467 209-0209-0

124124 123B123B SmithSmith 467467 102-8102-8

22nd nd Normal FormNormal FormThe RequirementsThe Requirements

The requirements to satisfy the 2The requirements to satisfy the 2ndnd NF:NF: All requirements for 1All requirements for 1stst NF must be met. NF must be met. Redundant data across multiple rows of Redundant data across multiple rows of

a table must be moved to a separate a table must be moved to a separate table.table.

The resulting tables must be related to each The resulting tables must be related to each other by use of foreign key.other by use of foreign key.

22nd nd Normal FormNormal Form Example ExampleStudents tableStudents table

Registration tableRegistration table

Student#Student# AdvIDAdvID AdvNameAdvName AdvRoomAdvRoom

123123 123A123A JamesJames 555555

124124 123B123B SmithSmith 467467

StudentStudent##

ClassClass##

123123 102-8102-8

123123 104-9104-9

124124 209-0209-0

124124 102-8102-8

33rdrd Normal Form Normal FormThe RequirementsThe Requirements

The requirements to satisfy the 3The requirements to satisfy the 3rdrd NF:NF: All requirements for 2All requirements for 2ndnd NF must be met. NF must be met. Eliminate fields that do not depend on Eliminate fields that do not depend on

the primary key;the primary key; That is, any field that is dependent not only That is, any field that is dependent not only

on the primary key but also on another field on the primary key but also on another field must be moved to another table.must be moved to another table.

33rdrd Normal Form Normal Form Example Example

Students table:Students table:

Student table:Student table: Advisor table:Advisor table:

Student#Student# AdvIDAdvID AdvNameAdvName AdvRoomAdvRoom

123123 123A123A JamesJames 555555

124124 123B123B SmithSmith 467467

StudentStudent##

AdvIAdvIDD

123123 123A123A

124124 123B123B

AdvIDAdvID AdvNamAdvNamee

AdvRooAdvRoomm

123A123A JamesJames 555555

123B123B SmithSmith 467467

33rdrd Normal Form Normal Form Example Cont. Example Cont.Students table:Students table:

Registration table:Registration table: Advisor table:Advisor table:Student#Student# Class#Class#

123123 102-8102-8

123123 104-9104-9

124124 209-0209-0

124124 102-8102-8

AdvIAdvIDD

AdvNamAdvNamee

AdvRooAdvRoomm

123A123A JamesJames 555555

123B123B SmithSmith 467467

StudentStudent##

AdvIAdvIDD

123123 123A123A

124124 123B123B

ConclusionConclusion

We have seen how Database We have seen how Database Normalization can decrease Normalization can decrease redundancy, increase efficiency and redundancy, increase efficiency and reduce anomalies by implementing reduce anomalies by implementing three of seven different levels of three of seven different levels of normalization called Normal Forms. The normalization called Normal Forms. The first three NF’s are usually sufficient for first three NF’s are usually sufficient for most small to medium size most small to medium size applications.applications.

ReferencesReferences

Hillyer Mike, MySQL AB. Hillyer Mike, MySQL AB. An Introduction to Database An Introduction to Database NormalizationNormalization, , http://dev.mysql.com/tech-resources/articles/intro-to-normalizationhttp://dev.mysql.com/tech-resources/articles/intro-to-normalization.html.html, accessed October 17, 2006., accessed October 17, 2006.

Microsoft. Microsoft. Description of the database normalization basicsDescription of the database normalization basics, , http://support.microsoft.com/kb/283878http://support.microsoft.com/kb/283878 , accessed October 17, , accessed October 17, 2006.2006.

Wikipedia. Wikipedia. Database Normalization. Database Normalization. http://http://en.wikipedia.org/wiki/Database_normalization.htmlen.wikipedia.org/wiki/Database_normalization.html , accessed , accessed October 17, 2006.October 17, 2006.