2 db sys concept

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2 db sys concept

  1. 1. Definition of Data model: * A set of concepts that can be used to describe the structure of a database: - 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.
  2. 2. Categories of data models Conceptual data model Logical data model Physical data model
  3. 3. • 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 perspective.
  4. 4. • Describes the data in as much detail as possible
  5. 5. • Specification all tables and columns. • Foreign keys are used to identify relationships between tables.
  6. 6. Categories of database models Flat database model Hierarchical database model Network database model Relational database model
  7. 7. • Consists of a single, two-dimensional array of data elements.
  8. 8. • 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- level list.
  9. 9. • Organizes data using two fundamental constructs, called records and sets. • Records contain fields hierarchically.
  10. 10. • 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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