January 10, 2011

DB Normalization in simple

This is one of the most frequently used question..lot times we know the thing have difficulty in expressing it...thot would write a simple post for it...

First Normal Form (1NF)
  • 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)

  • 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)

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

Fourth Normal Form (4NF)

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

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