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Database Normalization

Database Normalization.

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Database Normalization

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  1. Database Normalization The term Normalization is a process by which we can efficiently organize the data in a database. It associates relationship between individual tables according to policy designed both to care for the data and to create the database more flexible by eliminating redundancy and inconsistent dependency. Reason for normalization: to prevent possible corruption of DB stemming from update anomalies (insertion, deletion, modification).

  2. Functional and Fully Functional Dependencies • Functional Dependencydescribes the relationship between attributes in a relation. If A and B are attributes of a relation R, B is functionally dependent on A (den. A → B), if each value of A in R is associated with exactly one value of B in R. B is functional depend on A A B Full functional dependency: If A and B are attributes of a relation, B is fully functionally dependent on A if B is functionally dependent on A, but not any proper subset of A.

  3. Process of Normalization Unnormalized form (UNF): A table that contains one or more repeating groups. Repeating group: an attribute or group of attributes within a table that occurs with multiple values for a single occurrence of the nominated key attributes of that table.

  4. First Normal Form - 1NF • First normal form (1NF): A relation in which the intersection of each row and column contains one and only one value. • UNF → 1NF: remove repeating groups: • Entering appropriate data in the empty columns of rows. • Placing repeating data along with a copy of the original key attribute in a separate relation. Identifying a primary key for each of the new relations.

  5. First Normal Form - 1NF

  6. Second normal form (2NF) Second normal form (2NF): A relation that is in 1NF and every non-primary key attribute is fully functionally dependent on the primary key. 1NF → 2NF: remove partial dependencies: the functionally dependent attributes are removed from the relation by placing them in a new relation along with a copy of their determinant.

  7. Second normal form (2NF)

  8. Second normal form (2NF)

  9. Second normal form (2NF)

  10. Third Normal form (3NF) If relation that is in 3NF IFF the relation is in 2NF and all non key attributes are mutually independent

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