Comparison of Logical and Physical Data Modeling

Logical | Physical Data Modeling:

When a data modeler works with the client, his title may be a logical data modeler or a physical data modeler or combination of both. A logical data modeler  designs the data model to suit business requirements, creates and maintains the lookup data, compares the versions of data model, maintains change log, generate reports from data  model and whereas a physical data modeler has to know about the source and target databases properties.

A physical data modeler should know the technical-know-how  to create data models from existing databases and to tune the data models with referential integrity, alternate keys, indexes and how to match indexes to SQL code. It  would be good if the physical data modeler knows about replication, clustering and so on.

The differences between a logical data model and physical data model is shown below.

Logical vs Physical Data Modeling

Logical Data ModelPhysical Data Model
Represents business information and defines business rulesRepresents the physical implementation of the model in a database.
Primary KeyPrimary Key Constraint
Alternate KeyUnique Constraint or Unique Index
Inversion Key EntryNon Unique Index
RuleCheck Constraint, Default Value
RelationshipForeign Key

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