Database Normalization

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

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