What is Database normalization in MYSQL/SQL?

1. Introduction

a. Normalization is a step by step decomposition of complex records into simple records.
b. Normalization results in tables that satisfy some constraints and are simple represented in a manner.
c. This process is also called as canonical process synthesis.
d. This is a relation database design process to avoid data redundancy by applying some constraints on data to avoid various data anomalies.
e. Eg. If some information is repeated in multiple tables of database the there are chances that these tables will not be consistent in case of data updation, insertion or deletion. This instance may lead to problems of data integrity.

2. Definition

Normalization is a process of designing a consistent by minimizing redundancy and ensuring data integrity through decomposition which is lossless.

Goals of Database Normalization

1. Ensure Data Integrity

  • Data integrity ensure the correctness of data stored within the database
  • It is achieved by imposing integrity constraints.
  • An integrity constraint is a rule, which restricts values present in the database
  • Following are integrity constraints .

(i) Entity constraints

  • The entity integrity rule states that the value of the primary key can never be null value
  • Because a primary key is used to identify a unique row a relation table, its value must always be specific and should never be unknown.
  • The integrity rule requires that insert, update and delete operations maintain the uniqueness and existence of all primary keys.

(ii) Domain Constraints

Only permissible values of an attribute are allowed in relation.

(iii) Referential Integrity constraints

The referential integrity rule states that if a relational tables has a foreign key, then every value of the foreign key must either be null match the value in the relational table (referenced table) in which that foreign key is a primary key.

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