How to create a Logical Data Model:

In the following section, a simple example with a step by step procedure to create a logical data model with two entities and their relationship are explained in detail.

1: Open All Fusion Erwin Data Modeler software.

2: Select the view as "Logical" from the drop-down list. By default, logical will be your workplace.

3: Click New from File menu. Select the option "Logical/Physical" from the displayed wizard. Click Ok.

4: To create an Entity, click the icon "Entity" and drop it on the workplace. By default E/1 will be displayed as the entity name. Change it to "Country".

5: To create an Attribute, Place the cursor on the entity "Country" and right click it. From the displayed menu, click attributes which will take you to the attribute wizard. Click "New" button on the wizard and type attribute name as "Country Code". Select the data type as "String" and click OK. Select the option Primary Key to identify attribute "Country Code" as the primary key. Follow the same approach and create another attribute "Country Name" without selecting the primary key option. Click ok, and now you will be having 2 attributes Country Code, and Country Name under the entity "Country" in the current logical workplace.

6: Create another entity "Bank" with two attributes namely Bank Code and Bank Name by following steps 4 and 5.

7: In order to relate these two tables country, bank, a Foreign Key relationship must be created. To create a Foreign Key relationship, follow these steps.

(a) Click the symbol "Non Identifying Relationship".

(b) Place the cursor on the entity "Country".

(c) Place the cursor on the entity "Bank". Now you can see the relationship(a line drawn from Bank to Country) between "Country" and "Bank". Double click on that relationship line to open "Relationships wizard" and change the option from "Nulls Allowed" to "No Nulls" since bank should have a country code.

The Logical Data Model created by following the above steps looks similar to the following diagram.

Erwin Tutorial

All Fusion Erwin Data Modeler commonly known as Erwin, is a powerful and leading data modeling tool from Computer Associates. Computer Associates delivers several softwares for enterprise management, storage management solutions, security solutions, application life cycle management, data management and business intelligence.

Erwin makes database creation very simple by generating the DDL(sql) scripts from a data model by using its Forward Engineering technique or Erwin can be used to create data models from the existing database by using its Reverse Engineering technique.

Erwin workplace consists of the following main areas:

• 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, datatypes 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(rdbms, dbms, files etc.).
• 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 like .html, .rtf, and .txt.
• Data models can be opened and saved in several different file types like .er1, .ert, .bpx, .xml, .ers, .sql, .cmt, .df, .dbf, and .mdb files.
• By using ModelMart, concurrent users can work on the same data model.

In order to create data models in Erwin, you need to have this All Fusion Erwin Data Modeler installed in your system. If you have installed Modelmart, then more than one user can work on the same model.