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1Chapter 1 © Prentice Hall, 2002
Database DesignDatabase DesignDr. Bijoy BordoloiDr. Bijoy Bordoloi
Introduction to Database Processing
2Chapter 1 © Prentice Hall, 2002
DefinitionsDefinitions
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
3Chapter 1 © Prentice Hall, 2002
Figure 1-1a Data in Context
Large volume of facts, difficult to interpret or make decisions based on
4Chapter 1 © Prentice Hall, 2002
Figure 1-1b Summarized data
Useful information that managers can use for decision making and interpretation
5Chapter 1 © Prentice Hall, 2002
Table 1-1 Metadata
Descriptions of the properties or characteristics of the data, including data types, field sizes, allowable values, and documentation
6Chapter 1 © Prentice Hall, 2002
Figure 1-2 Three file processing systems at Pine Valley Furniture
Duplicate Data
7Chapter 1 © Prentice Hall, 2002
Problems with Data Problems with Data RedundancyRedundancy
Waste of space to have duplicate dataCauses more maintenance headachesThe biggest Problem:
– When data changes in one file, it could cause inconsistencies
– Compromises data integrity
8Chapter 1 © Prentice Hall, 2002
Disadvantages of File ProcessingDisadvantages 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
9Chapter 1 © Prentice Hall, 2002
Problems with Data DependencyProblems 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
10Chapter 1 © Prentice Hall, 2002
Problems with Data DependencyProblems 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?
11Chapter 1 © Prentice Hall, 2002
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
12Chapter 1 © Prentice Hall, 2002
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). . . . . .
13Chapter 1 © Prentice Hall, 2002
THE REPORT-PREPARATION PROGRAM
PROCEDURE DIVISION.*000-PREPARE-SALES-REPORT.*
OPEN INPUT CUSTMASTOUTPUT 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 CUSTMASTAT END
MOVE “Y”TO CUSTMAST-EOF-SWITCH.*
14Chapter 1 © Prentice Hall, 2002
Problems with Data DependencyProblems 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?
15Chapter 1 © Prentice Hall, 2002
SOLUTION: SOLUTION: The DATABASE ApproachThe DATABASE Approach
Central repository of shared dataData is managed by a controlling agentStored in a standardized, convenient
form
Requires a Database Management System (DBMS)
16Chapter 1 © Prentice Hall, 2002
Database Management Database Management SystemSystem
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.
17Chapter 1 © Prentice Hall, 2002
Database Management Database Management SystemSystem
DBMS manages data resources like an operating system manages hardware resources
DBMSDBMS Databasecontainingcentralized
shared data
Application#1
Application#2
Application#3
18Chapter 1 © Prentice Hall, 2002
Advantages of Database Approach 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
19Chapter 1 © Prentice Hall, 2002
Advantages of Database ApproachAdvantages of Database ApproachImproved 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
20Chapter 1 © Prentice Hall, 2002
Costs and Risks of the Costs and Risks of the Database ApproachDatabase 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
21Chapter 1 © Prentice Hall, 2002
The Range ofThe Range ofDatabase ApplicationsDatabase Applications
Personal Database – standalone desktop databaseWorkgroup Database – local area network (<25 users)Department Database – local area network (25-100 users)Enterprise Database – wide-area network (hundreds or
thousands of users)
22Chapter 1 © Prentice Hall, 2002
Components of the Components of the Database EnvironmentDatabase 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 Database 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
23Chapter 1 © Prentice Hall, 2002
Figure 1-10 Components of the database environment
24Chapter 1 © Prentice Hall, 2002
Evolution of DB SystemsEvolution of DB Systems
Flat files - 1960s - 1980sHierarchical – 1970s - 1990sNetwork – 1970s - 1990sRelational – 1980s - presentObject-oriented – 1990s - presentObject-relational – 1990s -
present