Normalization of Database
Normalization is a database
design technique which organizes tables in a manner that reduces redundancy and
dependency of data. It divides larger tables to smaller tables and links them
using relationships.
It is a systematic approach
of decomposing tables to eliminate data redundancy and undesirable characteristics
like insertion, update and deletion anomalies.
It is used for mainly two
purposes:
· Eliminating
redundant data.
· Ensuring
data dependencies make sense i.e. data is logically stored.
1NF: The following criteria’s
must be satisfied for 1NF -
1)
Each attribute of a table must have atomic
or single values and cannot hold multiple values.
2)
Each column must have unique name.
3)
No two rows are identical.
4)
No composite values.
5) All entries in any column must be of the same kind.
Example: Student Table,
|
Std.
Name |
Age |
Subject |
|
Adam |
15 |
Biology,
Chemistry |
|
Alex |
14 |
Mathematics |
|
Stuart |
17 |
Mathematics |
In 1NF from, any row must
not have a column in which more than one value is saved like separated with
commas. Rather than that, we must separate such data into multiple rows.
Student table following 1NF will be-
|
Std.
Name |
Age |
Subject |
|
Adam |
15 |
Biology |
|
Adam |
15 |
Chemistry |
|
Alex |
14 |
Mathematics |
|
Stuart |
17 |
Mathematics |
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