First normal form

Normal form describes the state of database when there is no redundancy or repetition of the same information. Bringing the relationship to the normal form is called database normalization. There are two basics rules without them Database Management System couldn’t work correctly and three more whose make a database more powerful and securable.

In the first post I want to focus on the first normal form.

First normal form

General definition:  Relationalship is in the first normal form if the values of each attributes are atomic and indivisible.

It’s mean that there is no complex type or grouped information. Picture 1 shows the wrong definition of a Sex table. There are  duplication of information in the one column.

Table before normalization

To solve this problem it is required to redesign this table in such a way that the sex of the different people would be inserted into single table and assigned them as a foreign key like on the picture below:

Table after normalization

Characteristics that must exist in the first normal form is that the key is defined in relationship and all attributes that are not key functional, dependence on key.