A quick summary of Database Normal Forms

So today in my study for exams, I worked out some simple ways of remembering up to Boyce-Codd normal form (BCNF).

  • 1st Normal Form: All rows/tuples must have the same number of columns/attributes.
  • 2nd Normal Form: Only applies to tables or schemas with composite keys, if it only has one key it is already in 2NF.
    A non-key column value must be relevant to ALL column values of the composite key. For example: on the table (keys are bolded) [Part Warehouse | Quantity | Warehouse Address] 2NF is violated as Warehouse Address is only related to Warehouse and not Part.
  • 3rd Normal Form: A non-key column can only be related to a key column. Modifying the earlier example to; [Part | Warehouse | Warehouse Address] this violates 3NF as Warehouse Address is related to Warehouse, not Part.
  • BCNF:

About Simeon Cheeseman

I enjoy a wide variety of computer and board games, have a BSc in Computer Science and have played percussion for 18 years.

Posted on June 17, 2010, in Database. Bookmark the permalink. Leave a comment.

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