Level6.pdf

Data Warehouse Introduction By Satish K Yellanki

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Document Prepared By The Technical Cell of

SkyEss Techno Solutions Pvt. Ltd., 80 / A, Flat No 201

Abhilash Towers, S.R. Nagar, Hyderabad : 500016. India

Phone : +91-040-23710047, [email protected]

Let us Start With CA-Erwin

Erwin Supports A Variety of Aspects of Database Design, Including Data

Modeling.

Erwin Supports Data Modeling in Two Flavors

Forward Engineering

The Creation of A Database Schema And Physical Database on The Basis of A

Data Model.

Reverse Engineering

The Creation of A Data Model on The Basis of An Existing Database.

Erwin Supports Data Modeling For A Wide Variety of Relational DBMS Software.

Main Areas of Erwin Workplace

Logical

In This View, Data Model Represents Business Requirements Like Entities,

Attributes Etc.

Physical

In This View, Data Model Represents Physical Structures Like Tables, Columns,

Data Types Etc.

Modelmart

Many Users Can Work With A Same Data Model Concurrently.

What Can Be Done With Erwin?

Logical, Physical And Dimensional Data Models Can Be Created.

Data Models Can Be Created From Existing Systems Like RDBMS, DBMS, Script

Files.

Different Versions of A Data Model Can Be Compared.

Data Model And Database Can Be Compared.

SQL Scripts Can Be Generated To Create Databases From Data Model.

Reports Can Be Generated in Different File Formats.

By Using Modelmart, Concurrent Users Can Work on The Same Data Model.

Starting CA-Erwin

Start Programs Computer Associates All Fusion Erwin Data Modeler

Erwin Data Modeler.

Step1 Creation of A Basic Data Model

Click The Create New Button OR File New OR CTRL + N.

In The Create Model Dialog Box Select Logical/Physical Option, And Any

Template if Available.

Select The Target Database As Oracle And Version As 10.x And Click OK.

NOTE

The Logical Model Does Not Allow The Target Database Selection.

The Physical Model Provides A List of Different Databases That Are Supported

By Erwin.

We Can Select Predefined Templates By Browsing The System if Available.


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Erwin Work Place

The Erwin Workplace Consists of Two Main Parts.

o The Model Navigator It Displays A Hierarchy of Items.

o The Display Window It Will Show The ER Diagram Itself.


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Setting Preferences

Erwin Accommodates A Number of Data Modeling Notations And Conventions.

To Set The Preferences, Click Model Model Properties

Few Options That Are Very Regular For Setting

From The Format Entity Display Menu, Make Sure That Primary Key

Designator is Checked

From The Format Entity Display Menu, Make Sure That Foreign Key

Designator (FK) is Unchecked.

From The Format Entity Display Menu, Make Sure That Show Migrated

Attributes is Unchecked.

From The Format relationship Display, Make Sure That Verb Phrase is

Checked.

We Can Choose Between Two Different ER Diagramming Notations From The

Model Properties Window

o Information Engineering Notation (IE)

o Integration DEFinition For Information Modeling IDEF1X.

Erwin Also Provides The Dimensional Modeling Notation.


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Steps To Create an Entity

To Create A New Entity, Click on The Entity Icon on The Erwin Toolbar And Click

in The Display Area, OR Right-Click on The Entities Node in The Model

Navigator.

Notice That The Default Name For The New Entity is E/x, Where x is Sequence

Number of The Entity.

Select The Entity in The Display Area And Click on The Tab Key To Focus The

Cycle Between The Three Main Parts of The Entity

o The Name of The Entity

o The Primary Key Attribute(s)

o The Non-Primary Key Attribute(s).

To Modify One of These Three Parts of The Entity, We Have To Press The Tab

Key To Cycle To The Appropriate Part of The Entity, Then Type To Add OR

Modify That Part of The Entity.

Steps To Add Primary Key Columns

Once The Entity Name is Changed, Then Press The Tab Key Again To Move The

Focus To The Next Part of The Entity, To Add A Primary Key Attribute.

Type The Name of The Primary Key Attribute As Per The Requirement of The

System Being Designed.

To Add Multiple Columns For A Primary Key, To Recognize As A Composite

Primary Key State, Press Enter Key After Adding The First Column For Primary

Key.

Steps To Add Non Key Attributes

Press The Tab Key After Adding The Primary Key Attribute, Which Will Help To

Add A Number of Non-Primary Key Attributes.

After Adding The Required Non-Primary Key Attribute Press The Enter Key, To

Add The Remaining Non Key Attributes.


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System For Design


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Creating Relationships in Erwin

Erwin Supports Three Basic Kinds of Relationship Types

o Identifying Relationship.

o Non-Identifying Relationship.

o Many-To-Many Relationship.

Erwin Supports Three Basic Kinds of Cardinality Types

o One-To-One

o One-To-Many

o Many-To-Many

Within The One-To-Many Category, Erwin Allows To Distinguish Between

Identifying And Non-Identifying One-To-Many Relationships.

Identifying Relationship

An Identifying Relationship is A Relationship Between Two Entities in Which An

Instance of A Child Entity is Identified Through its Association With A Parent

Entity.

In Identifying Relationship The Child Entity is Dependent on The Parent Entity

For its Identity And Cannot Exist Without The Parent Entity.

In An Identifying Relationship, One Instance of The Parent Entity is Related To

Multiple Instances of The Child.


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Notation Style in Erwin IDEF1X Notation

A Solid Line With A Diamond OR A Filled Circle At Either End of The Line.

IE Notation

A Solid Line With Crows Feet.

Steps To Create Identifying Relationship

To Create An Identifying Relationship, Click First on The Identifying

Relationship Icon.

Click on The Parent Entity, Generally on The One Side of The Relationship Entity

And Then Click on The Child Entity on The Many Side of The Relationship Entity.

Note

Erwin Provides A Label "R/x" For Every Relationship That is Created.

This Default Label Can Be Changed As Per Our Requirement in A Meaningful

Way.

Defining Customized Labels For Relationships

Double-Click on The Relationship To Open The Relationship Dialog Box.

The Relationship Dialog Box Has Features To Refine The Properties of The

Relationship.


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In The Relationship Text Box The Relationship is Presented From Parent Entity

R/1 Child Entity.

The Verb Phrase Portion of This Box Allows To Define The Label To Place on The

Relationship in Place of R/1.

In The Relationship Cardinality Portion, We Can Determine How Many Child

Entity Occurrences May Be Associated With Each Parent Entity Occurrence.

We Can Define Participation As Mandatory OR Optional in The Database.

Note

When An Entity Participates As The Child in An Identifying Relationship it is

Modeled With Rounded Corners.

This Notation is Useful To Understand The Weak Entity Concept in RDBMS.

Creating Non-Identifying Relationship

Click on The Non-Identifying Relationship Icon Which Uses A Dashed Line

Instead of A Solid Line.

Click On The Parent Entity, Then The Child Entity.

In Non-Identifying Relationship Type, We Have The Option of Indicating

Whether NULLS Are Permitted OR Not.

This Decision Regards The Participation of The Parent Entity in A Relationship

With The Child Entity.

We Have A Choice of Mandatory OR Optional State in Non-Identifying

Relationship.


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Creating Subtypes And Supertypes

Some Entities May Have Sub-Category Classifications.

Each of The Sub-Category Classifications Has All of The Properties of The Main

Category, But in Addition Have A Small Number of Specific Extra Attributes.

In Many Situations The Subtype Entities Do Not Contain Any Key Attributes.

The Attributes Registered in The Subtypes Are Only Registered To That Subtype

Entity And Should Not Be Part of The Main Type.

Subtype / Supertype Representation is For Clarity on The Overall System, But

Not Mandatory.

Steps in Erwin

To Specify The Sub Types Erwin Provides The Subtype Tool.

To Indicate A Subtype of Main Type, Select The Subtype Icon, Click on The

Super Type Entity, Then on The Subtype Entity.

To Represent The Additional Subtypes of The Same Maintype, Click on The

Subtype Icon That is Created And Then Click The Mouse on The Subtype Entity.


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Creation of A Database Schema

Before A Database Schema is Created We Must Ensure That All Fundamental OR

Strong Entities Have A Primary Key.

Once The Primary Keys Are Identified, We Should Define The Domain For Each

Attribute.

We Can Leave The Responsibility To Erwin For Converting The ER Diagram into

A Relational Schema.

Assigning Primary Keys

Fundamental OR Strong Entities Are Those That Do Not Depend on Any Other

Entity For Their Primary Key.

Fundamental Entities Are Not

o Subtypes

o Associative OR Composite Entities

o Weak OR Attributive Entities.

o Entities At The 'Many' End of An Identifying One-To-Many Relationship.


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The Sub-Types Do Not Contain Their Own Primary Keys, But They Inherit The

Primary Key From The Main Type.

Once The Primary Keys Are Identified For All The Strong Entities The Database

Schema Creation Can Be Commenced.

Defining Domains in Erwin

The Domain of An Attribute is The Set of Values That Attribute is Permitted To

Have.

To Define A Domain We Have To Define Two Components

Datatype

Datatype is A Mandatory Property Applied For Every Attribute.

Constraints

Constraints Are Optional Specifications Applied As Business Rules Upon The

Attributes.

Constraint Can Set The Permitted Values Which Can Be Narrower Than

Defined By The Data Type Alone.

Domains Can Be Shared By More Than One Attribute.


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In An ER Diagram, We Can Define The Domain Once, And Apply it to Multiple

Attributes.

Domains Provide The Benefit of Consistence Across Attributes And Ease of

Maintenance.

Steps To Create Domains

Click The Model Menu Domain Dictionary.

Specify The Required Options For Each Domain That Has To Be Created.

Steps To Create A Identifier Domain

To Create A New Domain Click on New Button.

Type The Logical Name of The Domain As Identifier And Click OK.

Click on The Data Type Tab, And Choose The INTEGER Datatype For This

Domain.


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Domains Identified For The Current Schema

After All The Required Domains Are Created, The Domains Are Individually

Attached To The Attributes.

Applying Domains To Attributes

The Final Step of Working With Domains is To Associate A Domain With Each

Attribute.

To Attach The Domain, Double-Click on One of The Entities in The E-R Diagram.

To Associated A Domain With An Attribute, Click First on The Attribute, Then

Click on The Associated Domain.

Converting An E-R Diagram into A Relational Schema

The First Stop in Converting An ER Diagram into A Relational Schema is To

Transform Each Entity And Each Relationship into its Counterpart in A

Relational Schema Consisting of Relational Tables.

Click Format Entity Display in Menu And Check The Following Properties

o Primary Key Designator

o Foreign Key Designator

o Show Migrated Attributes

To Transform The Logical ER Diagram into Physical Relational Schema Click And

Select The Physical Option.

In Physical Model The Relational Schema Will Be Looking Exactly As it is

Expected By The DBMS Software.


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Enhancing The Data Model

We Can Use The Drawing Features To Enhance The Data Model Appearance And

Make it Easier To View And Understand.

The Drawing And Appearance Features Provided Are

Enlarge The Font Size For All Entity Names.

Change The Color of All Foreign Keys To Red.

Use Different Fonts And Colors To Identify New Objects From Old Objects in

The Model.

Resize And Align One OR More Entity Boxes.


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Changing Font and Color For Individual Objects

Select The Object For Which The Font And Color Has To Be Changed And Use

Object Font And Color Property

Inheriting Objects With Color

In Erwin The Color of An Object Can Be Related To The Color it Inherits From

Other Objects in The Diagram.

Select The Relation Line And Click Secondary Mouse Button And Choose Object

Font And Color.


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Create Stored Displays

A Stored Display Helps in Having Different Views For The Data Model Very

Quickly.

Steps To Create Stored Display

Format Stored Display

In The Stored Displays Dialog Box Click New.

Type A Name For The Stored Display, And Click OK.

The New Stored Display Dialog Closes.

Select The Display Option Settings By Clicking The Property Tabs. Click OK To

Save.

Creating Subject Areas

A Subject Area is A Subset of Objects Taken From The Whole Pool of Objects in

The Model Diagram.

A New Data Model Includes One Subject Area Called The Main Subject Area,

Which Includes All of The Objects in The Data Model.

The Subject Areas Are Not Copies of The Data Model, But Are Dynamic Subsets

of The Data Model.

When A Members is Added To A Subject Area The Objects Are Added To The

Current Subject Area And The Main Subject Area.

When An Attribute OR Column is Added To An Existing Entity OR Table, The

New Object is Added To Every Subject Area in Which The Entity OR Table is A

Member.

Steps To Create A New Subject Area

Model Subject Areas OR Click The Subject Areas Button on The Toolbar.

In The Subject Area Editor, Click New.


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Type A Name For The New Subject Area, And Click OK.

Click The Members Tab And Use The Arrows To Include The Objects in The New

Subject Area, Click OK.

Creating An Index in The Index Editor

Right-Click A Table in The Diagram And Select Indexes (OR)

Right-Click An Index Located Under A Table in The Model Explorer And Select

Properties (OR)

Click An Index Located Under A Table in The Model Explorer, And Then Click

The Property Editor Button.

Click New, In The New Index Dialog Assign An Index Name.

Check The Unique Option To Create An AK Index OR Uncheck The Unique

Option To Create An Inversion Entry (IE) Index. Click OK.

In The Index Editor, Select The Index Columns From The Available Columns

List. Click OK.

Creating An Index in The Model Explorer

Click Tables To Expand The Folder, Right-Click The Indexes Folder.

Select Either New AK OR New IE, A New Folder With A Default Name is Added

To The Indexes List.


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Right-Click The New Index Folder, Select Properties.

Select The Index Columns From The Available Columns List, Click Close.

Creating Views in Erwin

We Can Create Views in Physical Model.

A View is A SQL Query Which is Permanently Stored In The Database Under

Assigned Names.

A View is Used To Present Specific Database Information For A Target

Audience.

In AllFusion ERwin Data Modeler, A View Table And Relationship Line Are Both

Drawn With Dashed-Lines.

Adding a View To A Model

Different Ways To Create A View in Erwin

o Click The Entity Button on The Allfusion Erwin DM Toolbox. Then Click in The

Diagram Window.

o Reverse Engineer An Existing Database.

o Copy A View From One Model And Paste it into Another Model.

o Right-Click The Views Folder in The Model Explorer And Choose New.

A View is A Logical Representation of The Data, That is Accessed From The

Database Table OR Tables.


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A View Provides Restricted Access To The Data From The Actual Database Table

OR Tables.

Forward Engineering

Forward Engineering is A Process That Generates The Physical Database

Schema From The Data Model.

Forward Engineering Process Can Generate A Schema

o Tables

o Triggers

o Stored Procedures

o Indexes

o Constraints

o Physical Storage Objects

o Other Database Features Supported By The Target DBMS.


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Through Forward Engineering A Data Model, We Can Choose To Generate A

Script File, Which We Can Use To Update The Database Using A Database

Administration Tool.

Using Forward Engineering We Can Directly Connect To The Database Catalog

And Generate The Database.

Before We Forward Engineer, We Can View The Schema, Which is A Text-Based

Representation of The Database Objects.

Preview Schema Generation

Select Open From The File Menu, And Open The Required Model For Schema

Generation.

Use The Model Type Indicator And Switch To The Physical Model.

Choose Forward Engineer, Schema Generation From The Tools Menu And Click

The Preview Button.

Change Schema Generation Options

We Can Set Schema Generation Options By Category.

The Target Server We Select Determines The Options That Appear in The Editor.

Tools Forward Engineer Schema Generator

Make The Necessary Selections As Per The Requirement.

Generate The Schema

From The Preview Dialog, Click Generate (OR)

From The Main Schema Generation Dialog, Click Generate.

In The Oracle Connection Dialog Box Enter A User Name, Password, And

Connect String.


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Level6.pdf