Normalization, Anomalies, decomposition

1. MCA, MSc(CS), PGDCA
Pratibha Rashmi

2.  NORMALIZATION is a database design
technique that organizes tables in a manner
that reduces redundancy and dependency of
data.
Normalization divides larger tables into Normalization divides larger tables into
smaller tables and links them using
relationships.
 The purpose of Normalization is to eliminate
redundant (repeated data) data and ensure
data is stored logically.

3.  Normalization ensures that the database is
structured i the best possible way.
 Reduce redundancy of data.
 To ensure data consistency where duplication
is necessary the data is the same.
 Remove insert, update and delete anomalies
of data.
 Storing the related attributes in the same
table.

4.  Update anomalies − If data items are scattered and
are not linked to each other properly, then it could
lead to strange situations.
 Deletion anomalies − We tried to delete a record,
but parts of it was left undeleted because ofbut parts of it was left undeleted because of
unawareness, the data is also saved somewhere else.
 Insert anomalies − We tried to insert data in a record
that does not exist at all.
Normalization is a method to remove all these
anomalies and bring the database to a consistent
state.

5. In normalization before decomposing a big
relation into several smaller once, one
should focused on two points:-
Lossless join decomposition-lossless Lossless join decomposition-lossless
decomposition ensures that no information is
lost from the original relation during
decomposition. When the sub relations are
joined back, the same relation is obtained
that was decomposed.Every decomposition
must always be lossless.

6.  Dependency Preservation- Dependency
preservation ensures that none of the
functional dependencies that holds on the
original relation are lost. The sub relations
still hold or satisfy the functional
dependencies of the original relation.