Database Systems - Relational & Flatfile and Definitions

  • Created by: lauren778
  • Created on: 10-04-18 13:24
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  • Database Systems
    • Flat file databases
      • Data is held in a single table, or in separate, unrelated tables.
    • Relational Databases
      • Definition
        • A large collection of data items and links between them, structured in such a way that it allows it to be accessed by a number of different application programs.
      • Organised to solve issues with Data Consistency, Redundancy, Integrity and Independence
    • Data Consistency
      • Where the same data has exactly the same value and formatting throughout, normally because it is only stored once.
    • Data Redundancy
      • When data is stored more than once. If data in one file is changed, it will also have to be changed in the other file or table.
    • Data Integrity
      • The correctness of the data. Problems could be avoided using validation and verification.
    • Data Independence
      • Keeping data separate from the applications which use it.
        • Eg. A booking system uses a DBMS to store bookings. Customers never see the complex DBMS - they use an internet-based front end.
    • Data Normalisation
      • A staged mathematical process which removes repeated groups of data and     inconsistencies.

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