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.

Data Modeling Tools: What to Learn?

Data modeling tools are the only way through which we can create powerful data models. Following are the various options that we have to know and learn in data modeling tools before start building data models.

Software:

» How to install the data modeling tool on server/client?

Logical Data Model:

» How to create entity and add definition, business rule?

» How to create domains?

» How to create an attribute and add definition, business rule, validation rules like default values
and check constraint?

» How to create supertypes, subtypes?

» How to create primary keys, unique constraint, foreign key relationships, and recursive relationships?

» How to create identifying and non-identifying relationship?

» How to assign relationship cardinality?

» How to phrase relationship connecting two tables?

» How to assign role names?

» How to create key groups?

» How to create sequence no's?

Physical Data Model:

» How to rename a table?

» How to rename a column,validation rules like default and check constraints?

» How to assign NULL and NOT NULL to columns?

» How to name foreign key constraints?

» How to connect to databases like MS Access, Oracle, Sibase, Terradata etc?

» How to generate sql code from data model to run against databases like MS Access, Oracle,
Sibase, Terradata etc.?

» How to create a data model from an existing database like MS Access, Oracle, Sibase, Terradata etc.?

» How to add database related properties to tables, indexes?

» How to check different versions of the data model?

» How many data modelers can concurrently work on the same version of a data model?