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
PROJNO PNAME BUD
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
PROJNO PNAME BUD
P1 Pn1 ------
P2 Pn2 ------
P3 Pn3 ------
EMP-INFO DEPT-INFO
EMPNO ENAME SAL DEPTNO DNAME LOC
11 ---- ---- 10 ------ -----
22 ---- ---- 20 ------ -----
33 ---- ----
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
PROJNO PNAME BUD
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
PROJNO PNAME BUD
P1 Pn1 ------
P2 Pn2 ------
P3 Pn3 ------
EMP-INFO DEPT-INFO
EMPNO ENAME SAL DEPTNO DNAME LOC
11 ---- ---- 10 ------ -----
22 ---- ---- 20 ------ -----
33 ---- ----
No comments:
Post a Comment