Ppt

1. Database
Management
System

2. Data Volume and Usage Analysis
Statistics about the size and usage
of data plays critical role in data
processing efficiency
Final step of logical DB design or
first step in physical DB design

3. Data Volume and Usage Analysis
Statistics collected during
analysis phase from the users of
the system
May not be accurate; give the
tentative and relevant figures

4. Data Volume and Usage Analysis

5. Composite Usage Map
PART
1000
MANUFAC-
TURED PART
PURCHASED
PART
O
QUOTATION
SUPPLIER
2500
40 % 70 %
50
140
200
60
40 80
75
(50) 40
70
700
400

6. Designing Fields
Field is smallest unit of application
data; corresponds to a simple
attribute
Involves different decisions about
fields

7. Choosing Data Type
Data type is defined as set of
values along with the operations
that can be performed on them
Precisely depends on the
particular DBMS

8. Choosing Data Types
Involves four objectives
– Minimize storage space
– Represent all possible values
– Improve data integrity
– Support all data manipulation

9. Coding Techniques
Values of the attributes with small
domains can be replaced by codes
Codes can be stored in lookup table
or can be hard coded, example

10. Coding Example
stId stName hobby
S1020 Sohail Dar Reading
S1038 Shoaib Ali Gardening
S1015 Tahira Ejaz Reading
S1015 Tahira Ejaz Movies
S1018 Arif Zia Reading
STUDENT

11. Coding Example
stId stName hobby
S1020 Sohail Dar R
S1038 Shoaib Ali G
S1015 Tahira Ejaz R
S1015 Tahira Ejaz M
S1018 Arif Zia R
code Hobby
R Reading
G Gardening
M Movies
STUDENT HOBBY

12. Controlling Data Integrity
Concerns the possible values that
a field can assume
First such control is enforced by
the data type
Some others are…

13. Controlling Data Integrity
Default value
Range control
Null values
Referential integrity
Handling missing data