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Database Normalization

Umasankar Natarajan
15/06/2017 0 0

Database Normalization is the process of reducing duplication in database by decomposing the table

1. Normal Form (1NF):

  • Every attribute is atomic, Each cell to be single valued
  • No multivalued attribute: Example subject  ( C, C++ )
  • No composite attribute: Example Address (392, XYZ street, Bangalore, 560001).  
  • Entries in a column are same type
  • Rows must be uniquely identified using UNIQUE ID or Add more column to make unique

2. Normal Form (2NF):
Table must not contain redundancy(Unnecessary repeating information).

3. Normal Form (3NF):
All fields can be determined only by Key in the table and not other column.

3.5. Normal Form - Boyce Codd Normal Form (BCNF):
Even when a database is in 3rd Normal Form, still there would be anomalies resulted if it has more than one Candidate Key. Table should not have multiple candidate key. Database should be only one primary key

4. 4NF (Fourth Normal Form):
Table instance contains two or more, independent and multivalued dependencies on Primary key

5. 5NF (Fifth Normal Form):
Table cannot be decomposed into any number of smaller tables without loss of data

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