Intro_toDB.ppt

Chapter 1 1
© Prentice Hall, 2002
Database Design
Dr. Bijoy Bordoloi
Introduction to Database
Processing

Chapter 1 2
Definitions
 Data: Meaningful facts, text, graphics,
images, sound, video segments
 Database: An organized collection of
logically related data
 Information: Data processed to be useful in
decision making
 Metadata: Data that describes data

Chapter 1 3
Figure 1-1a Data in Context
Large volume of facts, difficult
to interpret or make decisions
based on

Chapter 1 4
Figure 1-1b Summarized data
Useful information that managers can use for
decision making and interpretation

Chapter 1 5
Table 1-1 Metadata
Descriptions of the properties or characteristics of the
data, including data types, field sizes, allowable
values, and documentation

Chapter 1 6
Disadvantages of File Processing
 Data Redundancy (Duplication of data)
– Different systems/programs have separate copies of the same data
 Limited Data Sharing
– No centralized control of data
 Lengthy Development Times
– Programmers must design their own file formats
 Program-Data Dependence
– All programs maintain metadata for each file they use
 Excessive Program Maintenance
– 80% of of information systems budget

Chapter 1 7
Figure 1-2 Three file processing systems at Pine
Valley Furniture
Duplicate
Data

Chapter 1 8
Problems with Data
Redundancy
 Waste of space to have duplicate data
 Causes more maintenance headaches
 The biggest Problem:
– When data changes in one file, it could
cause inconsistencies
– Compromises data integrity

Chapter 1 9
Disadvantages of File Processing
 Data Redundancy (Duplication of data)
– Different systems/programs have separate copies of the same data
 Limited Data Sharing
– No centralized control of data
 Lengthy Development Times
– Programmers must design their own file formats
 Program-Data Dependence
– All programs maintain metadata for each file they use
 Excessive Program Maintenance
– 80% of of information systems budget

Chapter 1 10
Problems with Data Dependency
 Each application programmer must maintain their
own data
 Each application program needs to include code
for the metadata of each file
 Each application program must have its own
processing routines for reading, inserting, updating
and deleting data
 Lack of coordination and central control
 Non-standard file formats

Chapter 1 11
 Consider the following (partial) COBOL program
that produces a simple CUSTOMER SALES
REPORT based on the input data as shown.
 Carefully examine the structure of the input
record.
 How many Branches the company currently has at
the most?
 How many Salesperson the company currently
employs at the most?

Chapter 1 12
INPUT RECORD LAYOUT
Bytes Bytes Bytes Bytes Bytes Bytes
1-2 3-4 5-9 10-29 30-36 37-43
Branch
Number
Salesrep
Number
Customer
Number
Customer Name Sales this year-to-
date
Sales last year-to-
date
9(2) 9(2) 9(5) X(20) S9(5)V99 S9(5)V99
SAMPLE OUTPUT
Branch
Number
Salesrep
Number
Customer
Number
Customer Name Sales this year-to-
date
Sales last year-to-
date
12 12 11111 Information Builders 0123456 0111111
12 12 12345 Career Training Ctr 1234567 2222222
22 10 22222 Homelite Textrone Co 3454500 0000000
22 14 34567 Neas Member Benefits 0011111 0000000
22 14 55555 Pilot Life Ins. Co. 1000000 0100000
34 10 00111 Dauphin Deposit Bank 1409900 1993000
34 10 54321 Aircraft Owners Assc 0542612 4042000
34 17 33333 Norfolk Corp 0639635 0446288
47 11 12121 General Services Co. 1144400 1105956
47 11 24680 Info Management Co. 1748145 1189247
47 21 99999 Dollar Savings Bank 0505900 0462195
47 21 76543 Natl Music Corp 0238346 0443526

Chapter 1 13
A PARTIAL SAMPLE COBOL PROGRAM
.
.
FILE-CONTROL.
*
SELECT CUSTMAST ASSIGN TO CUSTMAST.
SELECT SALESRPT ASSIGN TO SALESRPT.
.
.
.
.
FILE SECTION.
*
FD CUSTMAST.
*
01 CUSTOMER-MASTER-RECORD.
05 CM-BRANCH-NUMBER PIC 9(2).
05 CM-SALESREP-NUMBER PIC 9(2).
05 CM-CUSTOMER-NUMBER PIC 9(5).
05 CM-CUSTOMER-NAME PIC X(20).
05 CM-SALES-THIS-YTD PIC S9(5)V9(2).
05 CM-SALES-LAST-YTD PIC S9(5)V9(2).
*
FD SALESRPT.
*
01 PRINT-AREA PIC X(132).
.
.
.
.
.

Chapter 1 14
THE REPORT-PREPARATION PROGRAM
PROCEDURE DIVISION.
*
000-PREPARE-SALES-REPORT.
*
OPEN INPUT CUSTMAST
OUTPUT SALESRPT.
PERFORM 100-FORMAT-REPORT-HEADING.
PERFORM 200-PREPARE-SALES-LINES
UNTIL CUSTMAST-EOF-SWITCH = ”Y”.
PERFORM 300-PRINT-GRAND-TOTALS.
CLOSE CUSTMAST
SALESRPT.
STOP RUN.
*
.
.
.
210-READ-CUSTOMER-RECORD.
*
READ CUSTMAST
AT END
MOVE “Y”TO CUSTMAST-EOF-SWITCH.
*

Chapter 1 15
 Assume, the company has grown and has decided
to open more branches and employ more
salespersons (>99).
 Assume, it is your responsibility as a company IS
manager to implement these required changes.
How will you go about implementing these
changes? What major bottlenecks you are likely to
encounter in implementing these simple changes?

Chapter 1 16
SOLUTION:
The DATABASE Approach
 Central repository of shared data
 Data is managed by a controlling agent
 Stored in a standardized, convenient
form
Requires a Database Management System (DBMS)

Chapter 1 17
Database Management
System
 A DBMS is a data storage and retrieval
system which permits data to be stored non-
redundantly while making it appear to the
user as if the data is well-integrated.

Chapter 1 18
Database Management System
DBMS manages data
resources like an operating
system manages hardware
resources
DBMS Database
containing
centralized
shared data
Application
#1
Application
#2
Application
#3

Chapter 1 19
Advantages of Database Approach
 Program-Data Independence
– Metadata stored in DBMS, so applications don’t need to worry
about data formats
– Data queries/updates managed by DBMS so programs don’t
need to process data access routines
– Results in: increased application development and maintenance
productivity
 Minimal Data Redundancy
– Leads to increased data integrity/consistency

Chapter 1 20
Advantages of Database Approach
 Improved Data Sharing
– Different users get different views of the data
 Enforcement of Standards
– All data access is done in the same way
 Improved Data Quality
– Constraints, data validation rules
 Better Data Accessibility/ Responsiveness
– Use of standard data query language (SQL)
 Security, Backup/Recovery, Concurrency
– Disaster recovery is easier

Chapter 1 21
Costs and Risks of the
Database Approach
 Up-front costs:
– Installation Management Cost and Complexity
– Conversion Costs
 Ongoing Costs
– Requires New, Specialized Personnel
– Need for Explicit Backup and Recovery
 Organizational Conflict
– Old habits die hard

Chapter 1 22
The Range of
Database Applications
 Personal Database – standalone desktop
database
 Workgroup Database – local area network
(<25 users)
 Department Database – local area network
(25-100 users)
 Enterprise Database – wide-area network
(hundreds or thousands of users)

Chapter 1 23
Components of the
Database Environment
 CASE Tools – computer-aided software engineering
 Repository – centralized storehouse of metadata
 Database Management System (DBMS) – software for
managing the database
 Database – storehouse of the data
 Application Programs – software using the data
 User Interface – text and graphical displays to users
 Data Administrators – personnel responsible for maintaining
the database
 System Developers – personnel responsible for designing
databases and software
 End Users – people who use the applications and databases

Chapter 1 24
Evolution of DB Systems
 Flat files - 1960s - 1980s
 Hierarchical – 1970s - 1990s
 Network – 1970s - 1990s
 Relational – 1980s - present
 Object-oriented – 1990s - present
 Object-relational – 1990s - present
 Data warehousing – 1980s - present
 Web-enabled – 1990s - present

Chapter 1 25
Figure 1-10
Components
of the
database
environment

Chapter 1 26
Figure 3
Figure 1-3 Segment from enterprise data model

Chapter 1 27
Figure 3
One customer may place many
orders, but each order is placed
by a single customer
 One-to-many relationship

Chapter 1 28
Figure 3
One order has many order
lines; each order line is
associated with a single order

Chapter 1 29
Figure 3
One product can be in many
order lines, each order line refers
to a single product

Chapter 1 30
Figure 3
Therefore, one order involves
many products and one product
is involved in many orders
 Many-to-many relationship

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