Download Introduction to Database

Database Design
Dr. Bijoy Bordoloi
Introduction to Database
Processing
Chapter 1
© Prentice Hall, 2002
1
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
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Figure 1-1a Data in Context
Large volume of facts, difficult
to interpret or make decisions
based on
Chapter 1
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Figure 1-1b Summarized data
Useful information that managers can use for
decision making and interpretation
Chapter 1
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Table 1-1 Metadata
Descriptions of the properties or characteristics of the
data, including data types, field sizes, allowable
values, and documentation
Chapter 1
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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
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Figure 1-2 Three file processing systems at Pine
Valley Furniture
Duplicate
Data
Chapter 1
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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
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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
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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
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Problems with Data Dependency

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
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INPUT RECORD LAYOUT
Bytes
Bytes
1-2
3-4
Branch
Salesrep
Number
Number
9(2)
9(2)
SAMPLE OUTPUT
Branch
Salesrep
Number
Number
12
12
12
12
22
10
22
14
22
14
34
10
34
10
34
17
47
11
47
11
47
21
47
21
Chapter 1
Bytes
5-9
Customer
Number
Bytes
10-29
Customer Name
Bytes
30-36
Sales this year-todate
Bytes
37-43
Sales last year-todate
9(5)
X(20)
S9(5)V99
S9(5)V99
Customer
Number
11111
12345
22222
34567
55555
00111
54321
33333
12121
24680
99999
76543
Customer Name
Information Builders
Career Training Ctr
Homelite Textrone Co
Neas Member Benefits
Pilot Life Ins. Co.
Dauphin Deposit Bank
Aircraft Owners Assc
Norfolk Corp
General Services Co.
Info Management Co.
Dollar Savings Bank
Natl Music Corp
© Prentice Hall, 2002
Sales this year-todate
0123456
1234567
3454500
0011111
1000000
1409900
0542612
0639635
1144400
1748145
0505900
0238346
Sales last year-todate
0111111
2222222
0000000
0000000
0100000
1993000
4042000
0446288
1105956
1189247
0462195
0443526
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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
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THE REPORT-PREPARATION PROGRAM
PROCEDURE DIVISION.
*
000-PREPA RE-SA LES-REPORT.
*
OPEN INPUT CUSTMAST
OUTPUT SA LESRPT.
PERFORM 100-FORMAT-REPORT-HEA DING.
PERFORM 200-PREPARE-SA LES-LINES
UNTIL CUSTMAST-EOF-SWITCH = ”Y”.
PERFORM 300-PRINT-GRA ND-TOTA LS.
CLOSE CUSTMAST
SALESRPT.
STOP RUN.
*
.
.
.
210-REA D-CUSTOM ER-RECORD.
*
READ CUSTMAST
AT END
MOVE “Y”TO CUSTMAST-EOF-SWITCH.
*
Chapter 1
© Prentice Hall, 2002
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Problems with Data Dependency

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
© Prentice Hall, 2002
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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
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Database Management
System

A DBMS is a data storage and retrieval
system which permits data to be stored nonredundantly while making it appear to the
user as if the data is well-integrated.
Chapter 1
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Database Management System
Application
#1
Application
#2
Application
#3
Chapter 1
DBMS
Database
containing
centralized
shared data
DBMS manages data
resources like an operating
system manages hardware
resources
© Prentice Hall, 2002
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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
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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
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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
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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
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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
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Evolution of DB Systems



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
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Chapter 1
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
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Figure 1-10
Components
of the
database
environment
Chapter 1
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Figure 1-3 Segment from enterprise data model
Figure 3
Chapter 1
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Figure 1-3 Segment from enterprise data model
Figure 3
One customer may place many
orders, but each order is placed
by a single customer
 One-to-many relationship
Chapter 1
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Figure 1-3 Segment from enterprise data model
Figure 3
One order has many order
lines; each order line is
associated with a single order
 One-to-many relationship
Chapter 1
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Figure 1-3 Segment from enterprise data model
Figure 3
One product can be in many
order lines, each order line refers
to a single product
 One-to-many relationship
Chapter 1
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Figure 1-3 Segment from enterprise data model
Figure 3
Therefore, one order involves
many products and one product
is involved in many orders
 Many-to-many relationship
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