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Chapter 8 Chapter 8 Presentation Transcript

  • David Morales
    Chapter 8
  • Normalization
    The process of organizing data in tables in a form that is useable in a data base
    Tasks involved in Normalization:
    Removing repetitive information
    Making sure each record occupies only one row
    Determining a piece of data that will uniquely identify each row
    Establish how each table’s data relates to other tables
  • Entity-Relationship Diagram (ERD)
    Model that shows logical relationships and interaction among system entities
    The Transaction liking the entities, logs hours on, is a third entity with its own characteristics, this entity is called an associative entity
    M and N denote the relationship as many to many
    Many employees may logs hours on different projects
    Logs hours on
    Employee
    Projects
    M
    N
    Time Keeping
  • ERD With Cardinality Notation
    The marks by the entities represent their cardinality
    Cardinality the numeric relationship and shows how instances of one entity relate to instances of another
    In the example one employee, or many employees, or none, can log hours on one project, many projects or no projects
    Logs hours on
    Employee
    Projects
    Time Keeping
  • Tables for Entities in 3NF
    Employee
    Projects
    Associates records in time keeping
    with records in Employee
    Associates records in time keeping
    with records in Projects
    Sum total of all hours in records in Time Keeping with corresponding the project #
    Time Keeping
  • Tasks
    Indentify all entities
    Create an initial ERD
    Assign all data elements to entities
    Verify all data dictionary entities
    Create tables in standard notation
  • Tasks
    Remove repeating groups (1NF)
    Remove fields from a table if not dependant on Primary key (2NF)
    Ensure every non-key field depend on the key, the whole key and nothing but the key
    Identify Keys
    Identify table relationships
  • Concurrent Tasks
    Identify all entities
    Assign all data elements to entities
    Verify all data dictionary entities
  • Sequential Tasks
    Create an initial ERD
    Create tables
    Identify keys
    1NF
    2NF
    3NF
    Identify table relationships