What is database Normalization?

[dtech-team]

Normalization is the process of efficiently organizing data in a database. There are two
goals of the normalization process: eliminating redundant data (for example, storing the
same data in more than one table) and ensuring data dependencies make sense (only
storing related data in a table). Both of these are worthy goals as they reduce the amount
of space a database consumes and ensure that data is logically stored.

[dtech-team]

First Normal Form (1NF)

First normal form (1NF) sets the very basic rules for an organized database:

• Eliminate duplicative columns from the same table.
  
• Create separate tables for each group of related data and identify each row with a unique column or set of columns (the primary key).
  

Second Normal Form (2NF)

Second normal form (2NF) further addresses the concept of removing duplicative data:

• Meet all the requirements of the first normal form.
  
• Remove subsets of data that apply to multiple rows of a table and place them in separate tables. 
• Create relationships between these new tables and their predecessors through the use of foreign keys.

Third Normal Form (3NF)

Third normal form (3NF) goes one large step further:

• Meet all the requirements of the second normal form.
  
• Remove columns that are not dependent upon the primary key.

Fourth Normal Form (4NF)

Finally, fourth normal form (4NF) has one additional requirement:

• Meet all the requirements of the third normal form.
  
• A relation is in 4NF if it has no multi-valued dependencies.

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SOURCE: http://databases.about.com/od/specificproducts/a/normalization.htm