What are the different types of normalization form?

@ : Home > > Interview Room

There are five types normal forms:

First normal form (1NF) sets the very basic rules for an organized database:

  • Eliminate duplicative columns from the same table.
  • Create separate tables for each group of related data and identify each row with a unique column or set of columns (the primary key).

Second normal form (2NF) further addresses the concept of removing duplicative data:

  • Meet all the requirements of the first normal form.
  • Remove subsets of data that apply to multiple rows of a table and place them in separate tables.
  • Create relationships between these new tables and their predecessors through the use of foreign keys.

Third normal form (3NF) goes one large step further:

  • Meet all the requirements of the second normal form.
  • Remove columns that are not dependent upon the primary key.

The Boyce-Codd Normal Form, also referred to as the "third and half (3.5) normal form", adds one more requirement:

  • Meet all the requirements of the third normal form.
  • Every determinant must be a candidate key. 

Fourth normal form (4NF) has one additional requirement:

  • Meet all the requirements of the third normal form.
  • A relation is in 4NF if it has no multi-valued dependencies.
Alert me