Physical Data Model - Dataware house

Physical Data Model
Physical data model represents how the model will be built in the database. A physical database model shows all table structures, including column name, column data type, column constraints, primary key, foreign key, and relationships between tables. Features of a physical data model include:

• Specification all tables and columns.
• Foreign keys are used to identify relationships between tables.
• Denormalization may occur based on user requirements.
• Physical considerations may cause the physical data model to be quite different from the logical data model.
• Physical data model will be different for different RDBMS. For example, data type for a column may be different between MySQL and SQL Server.

The steps for physical data model design are as follows:

1. Convert entities into tables.
2. Convert relationships into foreign keys.
3. Convert attributes into columns.
4. Modify the physical data model based on physical constraints / requirements.

The figure below is an example of a physical data model.

Physical Data Model

Comparing the physical data model shown above with the logical data model diagram, we see the main differences between the two:

• Entity names are now table names.
• Attributes are now column names.
• Data type for each column is specified. Data types can be different depending on the actual database being used.