Boyce-Codd Normal Form

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• Redundancy occurs when a column depends on another column that is not unique
• in Boyce-Codd normal form table, all dependencies are on unique columns
• dependence on a unique column never creates redundancy
  • so Boyce-Codd eliminates all redundancy arising from functional dependence
• third normal form applies to non-key columns only
  • which allows for occasional redundancy
• boyce-codd applies to all columns and eliminates this redundancy

A table is in Boyce-Codd normal form if, whenever column A depends on column B, then B is unique.

• Columns A and B may be simple or composite
• definition is identical to the definition of third normal form with the term ‘non-key’ removed
• considered the gold standard of table design

Trivial Dependencies

Dependencies are trivial when the columns of A are a subset of the columns of B, A always depends on B.

• must be excluded in definitions of normal form
  • a table is in Boyce-Codd normal form if, for all non-trivial dependencies B → A, B is unique