Definition of Data model:
* A set of concepts that can be used to describe the structure of
- data types, relationships, constraints,
semantics and operational behaviour.
* It is a tool for data abstraction.
Data model operations :
Specifying database retrievals and updates by referring to the
concepts of the data model.
Categories of data models
Conceptual data model
Logical data model
Physical data model
• Identifying the business concepts (entities)
• Relationships between these concepts in order to gain, reflect, and
document understanding of the organization’s business from a data
• Describes the data in as much detail as possible
• Specification all tables and columns.
• Foreign keys are used to identify relationships between tables.
Categories of database models
Flat database model
Hierarchical database model
Network database model
Relational database model
• Consists of a single, two-dimensional array of data elements.
• Data is organized into a tree-like structure, implying a single upward link
in each record to describe the nesting.
• A sort field to keep the records in a particular order in each same-
• Organizes data using two fundamental constructs, called records and sets.
• Records contain fields hierarchically.
• Allows the definition of data structures, storage and retrieval operations
and integrity constraints
• Organised in tables which is a collection of records and each record in a
table contains the same fields.
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