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Convert to Third Normal Form (3NF)

Sometimes within an entity we can find that there exists a "key" and "dependent" relationship between a group of non-key attributes. In our example above it is obvious in table 1 that this relationship exists between Tutor Id and Tutor Name. In this case they are removed to form a new table. If we did not perform the 3NF conversion then the course tutor's details (in this case, Name only) would be repeated each time this tutor's courses were stored. Here is the process:

  • Identify any dependencies between non-key attributes within each table
  • Remove them to form a new table
  • Promote one of the attributes to be the key of the new table
  • This becomes the Foreign Key link in the original table (shown with a *).

The following document shows this stage of Normalisation:

Next: Normalisation Activity