Normal Forms In Relational Database Theory

I was sitting here thinking about what else could I share that other DBAs and developers alike could use or need to know. Then it came to me!… Outside of a specific RDMS it definitely helps to know database theory. So today, I am going to cover Normal Forms or designated as (NF). In theory, as of right now there are 5 Normal Forms. For all practical use however most DBAs and developers take it to 3rd Normal Form. Knowing the Normal Forms and how to apply them will be a tremendous help when design your logical database model.   Edgar F. Codd originally defined the first three normal forms.  I have listed the Normal Forms for you below.

First Normal Form (1NF)
- Exclude variable repeating groups.

Second Normal Form (2NF)
- Meets all requirements of 1NF
- 2NF is violated when a non-key field is a fact about a subset of a key. It is only relevant when the key is composite.

Third Normal Form (3NF)
- Meets all requirements of 2NF
- 3NF is violated when a non-key field is a fact about another non-key field.

Fourth (4NF) and Fifth (5NF) Normal Forms deal with multi-valued facts. e.g. may correspond to a many-to-many relationship