What is normalazation,types with examples. with queries of all types?

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Permalink Reply by Sandip Wagh on July 20, 2010 at 3:56pm

Definition : normalization is organizing data in database.

There are 5 normal forms. It is necessary for any database to be in the third normal form to maintain referential integrity and non-redundancy.

1. First Normal Form: Every field of a table (row col) must contain an atomic value
2. Second Normal Form: All columns of a table must depend entirely on the primary key column.
3. Third Normal Form: All columns of a table must depend on all columns of a composite primary key.
4. Fourth Normal Form: A table must not contain two or more independent multi-valued facts. This normal form is often avoided for maintenance reasons.
5. Fifth Normal Form: is about symmetric dependencies.

Each normal form assumes that the table is already in the earlier normal form.

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Permalink Reply by Hitesh Shah on July 20, 2010 at 4:22pm

Hi

Thanks for reply , its nice explanation.
Hitesh
Noida

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Permalink Reply by vivek on July 21, 2010 at 12:53pm

After design of your DB . It is more imp. to ensure that data in table is consistent & relevant .

normalization is process of reducing the redundancy in the RDB (Relational Database )
normalization is a scientific approach of braking down complex table Structure into simple table structure by using certain rule

Using this method, You could reduce redundancy(repetition of data . It increase the time involve in updating, adding & delete data ) in table and eliminate the problem of inconsistency & disk space . You could ensure there is no loss of data

Advantages of normalization : Enable faster sorting
make database more compact
simplify structure
accelerator performance of database

Thumb rule of good database Design
# each table should have an Identifier
# each table should store data for single type of property
# columns that accepts NULLs should be avoided
# The repetitions of values / columns should be avoided

normalization result in the formation of table that satisfy certain specified rules & represent certain normal forms .

Idea of introduce normal forms ensure that various type of anomalies & inconsistencies are not introduced in DB.

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