Database Normalization 

This is a brief quick description of database normalization.

Database normalization is the process of organizing information in a relational database into tables to minimize redundancy.

Normalizing a database allows scalability and it is easier to maintain, query and work with.

There are 5 steps to normalize a database, my personal experience is that unless it is absolutely necessary, you are in best shape when you get to step four. Going to step 5 may decrease performance in your database.


There are 5 database normalization steps:

First Normalization Step
Eliminate duplicate columns on tables
Create separate tables for each groups
Identify primary keys for each row

Second Normalization Step
Remove subsets of data that apply to multiple rows of a table
Create  relationships between these new tables using foreign keys

Third Normalization Step
Remove columns that are not dependent on the primary key

Fourth Normalization Step
Every row must have a combination of attributes that can be uniquely identified without any extraneous data - primary key

Fifth Normalization Step
A relation is on Fourth Normalization when there are no rows with any duplicated data

Primary key: is a unique identifier for each record in a table. A primary key can comprise multiple fields, one informational field like email address or social security number,  or it can be generated by the database.

Foreign key: is a field or set of fields in one table that uniquely identifies a row of another number table: car color  or car color and year.

Relationships: a relationship exits between two tables, one has a foreign key referenced to another table.There are 3 relationship types:

• One to one: one to one relationships can only have one record on each side of the relationship: a car can only have one outside color
• One to many: one table can have multiple relations to another table: a car can have 2 or more interior colors
• Many  to  Many: tables can have multiple records related to multiple records on another table: a person can work at multiple companies, you need a third table to relate these kind of relationships