1. Database
Normalization

2. 7 Normal Forms Unnormalized data Normalized data 1NF 2NF 3NF BCNF 4NF
5NF (PJNF)‏
DKNF
Normalized data

3. Steps in normalization
Remove
Table with repeating groups
Repeating Groups
1st Normal Form
Partial Dependencies
2nd Normal Form
Transitive Dependencies
3rd Normal Form
Determinant / Candidate Keys
Boyce-Codd Normal Form
Multivalued Dependencies
4th Normal Form
Removing Remaining anomalies
5th Normal Form (Project Join NF)‏
Removing Remaining anomalies
Domain Key Normal Form

4. Boyce-Codd Normal Form
Determinant:
“A determinant is a simple or composite attribute that functionally determines one or more other attributes”.
A relation is in BCNF if and only if
“Every determinant is a candidate key”.
Y = f(X)‏ or
X = f(Y)‏
Y = mX + C
Determinant is X or Y
Dependent is X or Y

5. Boyce-Codd Normal Form
Process
All the determinants are identified.
If the determinants are candidate keys, the relation is in BCNF.

6. BCNF Consider DEPARTMENT relation with following attributes: DNO DNAME
Example with more than one candidate keys
Consider DEPARTMENT relation with following attributes:
DNO
DNAME
EMPS
MGR_NO
MGR_NAME 1
ACCT 10
100
ALI 2
ADMN 15
200
HASAN 3
FINANCE 20
300
KHAN 4
PROD 25
400
RAZA
This relation has three determinants:
DNO, DNAME and MGR_NO.
Each of the determinants is thus a candidate key.
So, the relation is in BCNF.

7. BCNF Consider SAM relation with following attributes: STID MAJOR
Example 2
Consider SAM relation with following attributes:
STID
MAJOR
ADVISOR 1
Database
Asad
S/w Engineering
Faisal 2
Comp. Communication
Imran 3
Zahid 4
In this relation, no single attribute is a candidate key.
That is, no single attribute is a determinant for the remaining two attributes.

8. BCNF This relation is not in BCNF because:
Example 2
This relation is not in BCNF because:
Although ADVISOR is a determinant, it is not a candidate key.
Although STID is a determinant, it is not a candidate key.
The combination (STID, ADVISOR) is a candidate key for this relation.
To convert into BCNF, divide this relation into two relations. The attribute that is a determinant but not a candidate key, must be placed in a separate relation and must be the key of that relation.

9. BCNF Relations in BCNF STID MAJOR ADVISOR MAJOR ADVISOR 1 Database
Asad
S/w Engineering
Faisal 2
Comp. Communication
Imran 3
Database
Zahid 4
Database
Asad

10. BCNF STID MAJOR ADVISOR STID ADVISOR ADVISOR MAJOR Relations in BCNF 1
Database
Asad
S/w Engineering
Faisal 2
Comp. Communication
Imran 3
Zahid 4
STID
ADVISOR 1
Asad
Faisal 2
Imran 3
Zahid 4
ADVISOR
MAJOR
Asad
Database
Faisal
S/w Engineering
Imran
Comp. Communication
Zahid

11. 4th Normal Form Let R be a relation with A, B and C as the attributes.
Multivalued Dependencies
Let R be a relation with A, B and C as the attributes.
There is a multivalued dependency of attribute B on attribute A if and only if the set of B values associated with a given A value is independent of the set of C values.
Easy
A type of dependency that exists when there are at least three attributes (Let A, B and C be the attributes) in a relation, and for each value of A there is a well defined set of values for B and a well defined set of values for C, but the set of values of B is independent of set of values of C.

12. 4th Normal Form Example Emp_no Salary Child_Name 1 10000 Ali Akram 2
20000
Babar
Elahi
Here Child_Name is dependent on Emp_no and is independent of Salary.
Emp_no determines salary because there is only one value of salary for each Emp_no. Salary depends on Emp_no.
Emp_no multidetermines Child_Name, because there can be several values of Child_name for each Emp_no.
Emp_no  Child_Name
Emp_no  Salary

13. 4th Normal Form Example COURSE INSTRUCTOR TEXTBOOK Table COURSE
DBMS
Ali
Akram
Babar
XYZ
ABC
C++
Sajid
PQR
JKL
Table
COURSE
INSTRUCTOR
TEXTBOOK
DBMS
Ali
XYZ
Akram
Babar
ABC
C++
Sajid
PQR
JKL
Relation

14. 4NF A relation is in 4th Normal Form if It is in BCNF and
It contains no multivalued dependencies.

15. 4NF Process Relation is in BCNF.
Divide the relation containing m/v dependencies into new relations.
Each of these relations contains attributes that have a multivalued relationship in the original relation.

16. 4th Normal Form Example Emp_no Child_Name Salary 1 Ali 10000 Akram 2
Babar
20000
Elahi
Emp_no
Child_Name 1
Ali
Akram 2
Babar
Elahi
Emp_no
Salary 1
10000 2
20000

17. 4th Normal Form Example COURSE INSTRUCTOR TEXTBOOK COURSE INSTRUCTOR
DBMS
Ali
XYZ
Akram
Babar
ABC
C++
Majid
PQR
JKL
COURSE
INSTRUCTOR
DBMS
Ali
Akram
Babar
C++
Majid
COURSE
TEXTBOOK
DBMS
XYZ
ABC
C++
PQR
JKL