Data Modeling is a representation of the data structures for a company database in a table and is a very powerful expression of the company business requirements. This data model is used as the guide by functional and technical analysts in the design and implementation of a database.
Three levels of Data Modeling are Conceptual, Logical and Physical Data Models.
Conceptual Data Model:
Conceptual data model identifies the highest-level relationships between the different entities.
Conceptual data model is designed by gathering business requirements from business documents, from discussions with business analysts, functional teams, smart management experts and the end users who do reporting on the database.
Conceptual Data Model Features:
Conceptual Data Model includes the important entities and the relationships among them.
No primary key is specified.
No attribute is specified.
Logical Data Model:
Logical Data Model describes the data as much as possible, regardless how they will be physically implemented in the database.
Logical Data Model is designed in the following steps:
Specifying primary keys for all entities.
Find relationships between different entities.
Find all attributes for each entity.
Resolve many-to-many relationships.
Logical Data Model Features:
Logical Data Model includes all entities and relationships among them
All Attributes, Primary key for each entity are specified.
Foreign keys are specified.
Normalization occurs in this level.
Physical Data Model:
Physical Data Model is a representation of a data design as implemented in the database management system. Physical Database Model shows all table structures, including primary key, foreign key, column name, column constraints, column data type, and also relationships between the tables.
Physical Data Model is designed in the following steps:
Convert entities into tables, relationships into foreign keys, attributes into columns.
Modify the physical data model based on physical constraints or requirements.
Physical Data Model Features:
Specification of all tables and columns.
Foreign keys are used to identify relationships between tables.
Physical considerations may cause the physical data model to be quite different from the logical data model.
Denormalization may occur based on user requirements.
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