|< < 24 > >|

Normal Forms

A normal form is a rule about a table, usually involving dependencies. If the rule applies, then some kinds of anomalies are avoided.

First normal form (1NF)

Column types are simple values

  • This rules out hierarchical data models.
  • Tables are 1NF by definition.

Second normal form (2NF)

Terminology: non-prime column

A non-prime column is a column that does not belong to any candidate key.

2NF

A relation is in 2NF if:

  • It is 1NF, and
  • For every candidate key K, every non-prime column is dependent on all of K, (and not a subset of K).

|< < 24 > >|