Normalization & denormalization

Normalization

• 1^st Normal from removes repetition by creating one-to-many relationship
• 2^nd Normal from separating static from dynamic information by creating many-to-one relationship
• 3^rd Normal from resolve many-to-many relationship into unique values by creating of additional many-to-many join resolution tables
• 4^th Normal from minimize nulls by separating multivalued facts in a single table into multiple tables
• 5^th Normal composite primary keys by removing null fields and subset composite primary key dependent to new tables

Denormalization

• Normalization in reverse
• Data warehousing
• Separating different usage data
• Performance problems
• over complex table structure
• complicated multiple tables joins
• separate different usage data
• reporting against application tables

What it is?

• Normalization in reverse
• Data warehousing
• Separating different usage data

Why?

• Performance problems 
• over complex table structure 
• complicated multiple tables joins 
• separate different usage data 
• reporting against application tables