Entity Relationship Modeling using ERwinTo start ERwin, click on StartProgramsCAERwinERwin Data Modeler r9ERwin Dtata Modeler.

The first time you use ERwin, a screen similar to the one below will appear. Under “Concurrent Licenses”, select the “Acquire concurrent use Standard Edition license option and provide the server path as specified in the screenshot below.

Initial SettingsPrior to creating our entities and relationships, configure the necessary settings to optimize your view of the model. First, change your workspace properties to display keys, data types and relationship names.

To display the attribute data type, right click on an empty area in the workspace and select “Properties”. Under the “Entity” tab at the bottom, check the options to “Display Attribute Data Type” and “Display Logical Primary Key (PK) Designator”. Under the “Relationship” tab, check the option to “Display Logical Relationship Name” and “Display Physical Relationship Name”. Close the properties window.

Before creating a relationship, ensure that your model is configured to display “Crow’s Foot” notation. To do this, click on the “Model” menu and select “Model Properties”. In the “Model Properties” dialog, choose “Information Engineering” as the logical and physical notation.

Creating a new modelTo create a new data model, Click on FileNew.

Select Logical/Physical as the model type. Other fields can be left with default values, or can select the target server based on the DBMS platform for which you are modeling.

A screen similar to the one below will appear. You are ready to start modeling!

Representing Entities and AttributesTo create a new entity, click on the Entity icon and then click a location in the blank workspace.

A new Entity will be displayed in the workspace.

Alternately, you can right-click in the Model Explorer on “Entities” and select “New”

A new entity will be created under the Entities in Model Explorer, which you can click and drag into the workspace.

Edit the default entity name by clicking on the entity name and entering a more descriptive name as shown below. Alternately, the entity name can be edited by opening the entity editor. Double clicking the entity will open the editor.

Create two entities, named “Band” and “Album”.

Defining AttributesPrimary key attributes will be displayed in the upper portion of each entity (above the line) and remaining attributes will be displayed in the lower portion of each entity. To define attributes, right-click the entity in the workspace and choose “Attribute Properties”.

The following screen will appear. To create attributes, click the “New” icon and enter the information for each attribute as appropriate.

After entering the attributes for both entities, the workspace should look similar to the one below. If you wish to change the properties of an attribute, right click on the entity or attribute and select the appropriate option to edit the properties.

Representing RelationshipsRelationships between entities can be created as identifying, non-identifying, and many-to-many. Most relationships will be created as non-identifying. Create a non-identifying relationship between Band and Album by clicking the “Non-identifying relationship” icon on the toolbar, then clicking on the “Band” entity and dragging the relationship onto the “Album” entity. Alternately, in the “Model Explorer” window, right-click “Relationships” and select “New”. Band will be the parent and Album will be the child in this relationship (be sure to change the relationship type here as well).

Note that a Foreign Key (FK) attribute was automatically created in the child table (Album in this example), and the name of the relationship was populated by a default value. To change the name of this relationship, double-click on the name to edit it, or open the properties screen for the relationship and edit it from there. Note two other important settings on the relationship properties screen.

The “Null Option” selection will indicate whether null values are allowed in the FK field. If you wish for the cardinality on the “one” side of the relationship to be mandatory, select “Nulls Not Allowed”, meaning that any record in the child table (Album in this example) must be associated with a record in the parent table (Band in this example).

To specify the cardinality on the “many” side of the relationship, select the appropriate option from the “Cardinality” selection list: “Zero, One or More” for one-to-optional-many, “One or More (P)” for one-to-mandatory-many, or “Zero or One (Z)” for one-to-optional-one.

You have created your first data model using ERwin! Now save your work (if you haven’t already) . Instructions for saving are below.

Saving the Data ModelFrom the “File” menu, select “Save As” and navigate to the folder where you want to save the model.

Exporting to PDFTo export your model to PDF, click on the “Tools” menu and select “Pinned ReportsCurrent Diagram Membership (Logical).rpt”

On the following screen, click on the “File” menu and select “Export”.

Under “Save as type”, select “PDF (*.pdf). Then, navigate to the folder where you want to save the PDF, enter a name for the file, and click “Save”.