Tuesday, September 2, 2014

Third Normal Form (3NF)

Remove transitive dependencies
Transitive dependency
  • A non-prime attribute is dependent on another, non-prime attribute or attributes
  • Attribute is the result of a calculation


Examples:
  • Area code attribute based on City attribute of a customer
  • Total price attribute of order entry based on quantity attribute and unit price attribute (calculated value)


Solution:
  •  Any transitive dependencies are moved into a smaller table.


Transitive Dependence



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