Database Normalization Basics

There are two goals of the normalization process: eliminate redundant data (for example, storing the same data in more than one table) and ensure data dependencies make sense (only storing related data in a table). Both of these are worthy goals as they reduce the amount of space a database consumes and ensure that data is logically stored.

Some of the benefits of normalization include:

  • Faster sorting and index creation.
  • A larger number of clustered indexes. Narrower and more compact indexes.
  • Fewer indexes per table, which improves the performance of INSERT, UPDATE, and DELETE statements.
  • Fewer null values and less opportunity for inconsistency, which increase database
    compactness.

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. Finally, 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.

Remember, these normalization guidelines are cumulative. For a database to be in 2NF, it must first fulfill all the criteria of a 1NF database.

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