On Normalization

People have funny ideas about database normalization.

What normalization is not:

  • creating an (id,value) table for every single piece of data is not normalization
  • using surrogate keys for everything is not normalization
  • a way to improve performance (though it sometimes does)

Equally, failing to do the above does not mean your data is “denormalized”.

What normalization is:

  • keeping your data consistent by ensuring that the relationships between values exist only in one place
  • applying the rules: 1NF, 2NF, 3NF, BCNF, 4NF, 5NF … usually between 3NF and 4NF is enough

Obviously, though, there are times when one denormalizes for performance reasons, with appropriate care to ensure consistency isn’t lost in the process.

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