Demoralization

The end product of normalization is a set of related tables that comprise the DB. The virtues of normalization have already been enumerated. Thus, sometimes, to obtain a simple output you have to join multiple tables. This will affect the performance of a query. In those cases it is wiser to introduce a degree of redundancy in tables either through introducing extra tables or extra columns.The intended introduction of redundancy in a table in order to improve performance is known as demoralization.

For instance, let consider the following tables that maintain the details of tables

Select * from department join employee on department.MGRSSN = employee.SUPERSSN;

This table structure has simplified the query and speeded up the processing of the query. Through storing extra columns you are introducing redundancy in the table but improving the performance of queries.The decision to denormalize will obliviously result in a trade-off among data integrity and performance. Denormalization also raises disk space utilization.