Normalization and its Types

Normalization is the process of organizing data into a related table; it also eliminates redundancy and increases the integrity.

Update Anomaly - Cannot update information without changing information in many places. To update customer information, it must be updated for each sales order the customer has placed.

DE- NORMALIZATION: 
Denormalization is the process of adding redundant data to speed up complex queries involving multiple table JOINS. One might just go to a lower form of Normalization to achieve Denormalization and better performance. Data is included in one table from another in order to eliminate the second table which reduces the number of JOINS in a query and thus achieves performance.

First Normal Form (1st NF)

• The table cells must be of single value.
• Eliminate repeating groups in individual tables.
• Create a separate table for each set of related data.
• Identify each set of related data with a primary key.

Definition: An entity is in the first normal form if it contains no repeating groups.

Second Normal Form (2nd NF)

• Remove Partial Dependencies.
• Functional Dependency: The value of one attribute in a table is determined entirely by the value of another.
• Partial Dependency: A type of functional dependency where an attribute is functionally dependent on only part of the primary key (primary key must be a composite key).

Definition: A relation is in 2NF if it is in 1NF and every non-key attribute is fully dependent on each candidate key of the relation. 
Third Normal Form (3rd NF)

• Remove transitive dependencies.
• Transitive Dependency A type of functional dependency where an attribute is functionally dependent on an attribute other than the primary key. Thus its value is only indirectly determined by the primary key.

A relation is in third normal form, if it is in 2NF and every non-key attribute of the relation is non-transitively dependent on each candidate key of the relation

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