Database Normalization

Databases are either unnormalized, or normalized according to five levels of rules.

• First Normal Form
  • Eliminate repeating groups in individual tables.
  • Create a separate table for each set of related data.
  • Identify each set of related data with a primary key.
• Second Normal Form
  • Create separate tables for sets of values that apply to multiple records.
  • Relate these tables with a foreign key.
• Third Normal Form
  • Eliminate fields that do not depend on the key.
• Fourth Normal Form
  • In a many-to-many relationship, do not store independent entities in the same table.
• Fifth Normal Form
  • You must be able to reconstsruct the original table from the tables into which it has been broken down.