How to Implement Third Normal Form

In this article I am going to explain how to Implement third normal form in SQL.
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Introduction

Normalization is used to organize the content of table. Normalization is a technique which eliminate redundancy and inconsistent dependency of data from database. Normalization makes database more flexible.

Basic Goal of normalization

  • Arrange data in database in to logical grouping.
  • Eliminate redundancy of data, it means minimizing the duplicate data in database.
  • Eliminate inconsistency of data 

Third Normal Form

For a table in third normal from it must be in second normal form and every non-key column must depend only on the primary key. Third normal form is based on concept of transitive dependency.  In other word we can say no non prime attributes functionally dependent on other non prime attribute.

Example

In this table data is in second normal form but not in third normal form.  In this table non prime attributes are not fully dependent on primary key (project number).

Table in Second Normal Form but not in Third Normal Form

Project_Number Project_Manager Address
 P0086   Vipendra  Nehru Place, Delhi
 P0096  Deepak   Sector 19, Noida

Now we divide this table in three different tables and these tables are in third normal form.

Table 1

Project_Number Project_Manager
 P0086   Vipendra
 P0096  Deepak

Table 2

Project_Manager Address
  Vipendra  Nehru Place, Delhi
 Deepak   Sector 19, Noida

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