Lecture Slide by Md. Masudur Rahman, Lecturer, Khulna University, Bangladesh

1. Designing Databases
Md. Masudur Rahman
Lecturer
CSE, KU

2. Contents
 Overview
 RDBM
 Normalization
 Well structured Relation
 Functional Dependency
 Second Normal Form (2NF)
 Examples

3. Overview
 Process and Data modeling parallel
 Logical Design of database first
 Structure data requirements
 Stable State

4. RDBM (Relational Database Model)
 Network, hierarchical, OO Model
 RDBM- data in the form of related tables or
relations
 Relation- 2 dimensional data with fixed no of
columns and arbitrary no of rows
 Each column represents an attribute of an
entity

5. Normalization
 Arbitrary data difficult to manage
 Converting the relation containing redundant
info into simple structure with minimum
redundancy – normalization
 2 standards- 2NF and 3NF

6. Well Structured Relation
 Relation with minimal redundancy
 Facilitating all CRUD operation without errors
or inconsistency
 Removing redundancy- normalization is
based on the analysis of functional
dependency

7. Functional Dependency
 Relationship between any two attributes of a
relationship
 Not like y=f(x) where value of y can be
computed from x
 If two attributes A, B, then B is said to be
functionally dependent on A if for each
distinct value of A, B has a distinct/separate
value. And notation is A->B

8. Example (FD)
A B C D
X U X Y
Y X Z X
Z Y Y Y
Y Z Z Z
A->C

9. Second Normal Form
 Each non-primary key attribute is functionally
dependent on the whole key/primary key
 3 conditions for 2NF- any one needs to be
satisfied
 A redundant relation can be decomposed
using determinants

10. Example (2NF)
 EMPLOYEE1: {Emp_ID, Name}
 EMPLOYEE2: {Emp_ID, Name, District}
 EMPLOYEE2 is not in 2NF, so it needs to be
decomposed using determinants which
determines the entity
 - {Emp_ID, Name} and {Emp_ID, District}

11. Thanks