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NORMALIZATION
NORMALIZATION
Normalization is process of splitting the base table into
multiple tables based on the theory of Functional Dependency.
OR
Normalization is repetitive process in order to identify the
functional dependencies among the columns and to remove them. If
any functional dependency is occurred after the normalization
process again we have to start the same process until all
functional dependencies have been removed.
To do this Normalization we have to follow rules or conditions
called Normal Forms.
Un-Normalized Table
EMPNO PROJNO ENAME PNAME SAL BUD DEPTNO DNAME LOC
11 (P1, P2) ---- (Pn1, Pn2) ----- ----- 10 -------- -----
22 (P2, P3) ---- (Pn2, Pn3) ----- ----- 10 -------- -----
33 (P1, P3) ---- (Pn1, Pn3) ----- ----- 20 -------- -----
EMPNO and PROJNO are Primary Keys called COMPOSITE PRIMARY
KEY
FIRST NORMAL FORM (1NF): According to first normal form table
should contain only single values columns. But in the above
un-normalized table the columns PROJNO and PNAME contains multiple
values.
To make the table into first normal form we should have to split
the multiple values into single values.
EMPNO PROJNO ENAME PNAME SAL BUD DEPTNO DNAME LOC
11 P1
---- Pn1 ----- ----- 10 -------- -----
11 P2
---- Pn2 ----- ----- 10 -------- -----
22 P2
---- Pn2 ----- ----- 10 -------- -----
22 P3
---- Pn3 ----- ----- 10 -------- -----
33 P1
---- Pn1 ----- ----- 20 -------- -----
33 P3
---- Pn3 ----- ----- 20 -------- -----
SECOND NORMAL FORM (2NF):
According to second normal form table should be in 1NF and we
should have to remove Partial Functional Dependency.
In the above table DEPTNO non-key column dependent part of the
Primary key column i.e.EMPNO. It means there existed Partial
functional dependency.
To make the table into second normal form we have to divide the
table into multiple tables.
PROJ-INFO
PROJNOPNAMEBUD
P1
Pn1
------
P2
Pn2
------
P3
Pn3
------
EMP-INFO
EMPNO ENAME SAL DEPTNO DNAME LOC
11 ---- ---- 10 ------ -----
22 ---- ---- 10 ------ -----
33 ---- ---- 20 ------ -----
THIRD NORMAL FORM (3NF):
According to second normal form table should be in 2NF and we
should have to remove Transitive Functional Dependency.
In the above EMP-INFO table non-key column DNAME dependent part
on the other non- key column i.e.DEPTNO. It means there existed
Transitive functional dependency.
To make the table into third normal form we have to divide the
table into multiple tables.
PROJ-INFO
PROJNOPNAMEBUD
P1
Pn1
------
P2
Pn2
------
P3
Pn3
------
EMP-INFO DEPT-INFO
EMPNO ENAME SAL DEPTNO DNAME LOC
11 ---- ---- 10 ------ -----
22 ---- ---- 20 ------ -----
33 ---- ----
