Db sys concept

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Db sys concept

  1. 1. Contents: 1. Data Models 2. Schemas 3. Database Architecture 4. Database Languages 5. Database Interfaces
  2. 2.  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.
  3. 3.  Categories of data models  Conceptual data model  Logical data model  Physical data model
  4. 4. 1-1. Data models (Conceptual 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 perspective.
  5. 5. 1-1. Data models (Logical data model) • Describes the data in as much detail as possible
  6. 6. 1-1. Data models (Physical data model) • Specification all tables and columns. • Foreign keys are used to identify relationships between tables.
  7. 7.  Categories of database models  Flat database model  Hierarchical database model  Network database model  Relational database model  Object/Relational database model  Object-oriented database model
  8. 8. 1-2. Database models (Flat DB model) • consists of a single, two-dimensional array of data elements. • all members of a given column are assumed to be similar values. • all members of a row are assumed to be related to one another.
  9. 9. 1-2. Database models (Hierarchical DB model) • Organized into a tree-like structure • A sort field to keep the records in a particular order in each same-level list. • widely used in the database management systems.
  10. 10. 1-2. Database models (Network DB model) • Records and sets are using as fundamental constructs. • Records contain fields, Sets define one-to-many relationships between records.
  11. 11. 1-2. Database models (Relational DB model) • Allows the definition of data structures, storage and retrieval operations and integrity constraints. And organised in tables. • Records and each record in a table contains the same fields.

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