Physical Data Model




Data Warehousing > Concepts > 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

Physical Data Model

Comparing the logical 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.





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