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

1Chapter 1 © Prentice Hall, 2002

Database DesignDatabase DesignDr. Bijoy BordoloiDr. Bijoy Bordoloi

Introduction to Database Processing


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


Figure 1-1a Data in Context

Large volume of facts, difficult to interpret or make decisions based on


Figure 1-1b Summarized data

Useful information that managers can use for decision making and interpretation


Table 1-1 Metadata

Descriptions of the properties or characteristics of the data, including data types, field sizes, allowable values, and documentation


Figure 1-2 Three file processing systems at Pine Valley Furniture

Duplicate Data


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


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


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


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?


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


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). . . . . .


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.*


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?


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)


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.


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


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


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


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


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)


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


Figure 1-10 Components of the database environment


Evolution of DB SystemsEvolution of DB Systems

Flat files - 1960s - 1980sHierarchical – 1970s - 1990sNetwork – 1970s - 1990sRelational – 1980s - presentObject-oriented – 1990s - presentObject-relational – 1990s -

present

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

Documents

data limited data

data changes

data dependency

input data

prentice hall

data types

definitions data

related data information