How to normalise logical data models

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Do any attributes have multiple values for a single instance of an entity?

0. Unnormalised Form

Yes - remove the repeating attributes and repeating groups. Create an entity that describes the attributes. Often you will need to add a relationship to connect the old and new entities.

No - the data model is in first normal form.

1. First Normal Form

Is the identifier composed of more than one attribute? If so, are any attribute values dependent on just one part of the identifier?

Yes - remove the partial dependency. Move attributes to an entity in which their values are dependent on the entire identifier. Usually you will need to create a new entity and add a relationship to connect it to the old.

No - the data model is in second normal form.

2. Second Normal Form

Do any attribute values depend on an attribute that is not the entity's identifier?

Yes - remove the transitive dependency or derived attribute. Move the attributes to an entity in which their values are dependent on the identifier. Create a new entity and a relationship that links it to the old entity.

No - the data model is in third normal form.

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