7.1 © 2006 by Prentice Hall Managing Data Resources Md. Rashedul Hasan.

7.1 © 2006 by Prentice Hall

Managing Data Managing Data ResourcesResources

Managing Data Managing Data ResourcesResources

Md. Rashedul Hasan


Data and Organizations

For various reasons, organizations collect and store vast amounts of data about employees, customers, finances, vendors, inventory, competitors, and markets, to name only a few. The amount of data needed is important because people generally make better decisions if they have more data available to them.



For example, a car dealership, bank, or credit union will make better decisions about who to give car loans by looking at a person's credit report information than if they simply based their decision on the word of the customer. Looking at your credit report, a bank representative would see a listing of your payment history on loans and credit cards, including your mortgage. She would also see information about outstanding loans, debt repayment and credit limits. The report may also contain information about jobs you have held and public record information (birth date and address).



To help ensure "appropriate" customer service, some companies have initiated a grading system for their customers. Customers that make the company a lot of money, or are highly valued customers, receive an A-rating. A B-rating is given to mediocre customers and a C-rating is reserved for customers with bad credit or "bad" dispositions on previous customer service calls. This requires the company to store data on their customers and helps the customer service representatives know which customers are most highly valued and therefore deserve the best service.


The Data HierarchyThe Data Hierarchy

• The computer system organizes data in a hierarchy that starts from Bit.

• Bit: Smallest unit of data; binary digit (0,1) • Byte: Group of bits that represents a single character.

Basically 8 bits is equal to 1 Byte. • Field: Group of words or a complete number • Record: Related fields can be Grouped to form a

record. • File: Group of records of same type

ORGANIZING DATA IN A TRADITIONAL FILE ENVIRONMENT


• Database: Group of related files

• Entity: Person, place, thing, event about which information is maintained

• Attribute: Description of a particular entity

• Key field: Identifier field used to retrieve, update, sort a record


File Organization Terms and Concepts (Continued)File Organization Terms and Concepts (Continued)



The Data Hierarchy

Figure 7-1



Entities and Attributes

Figure 7-2


Problems with the Traditional File Environment

Data Redundancy and Inconsistency: • Data redundancy: The presence of duplicate data

in multiple data files so that the same data are stored in more than one place or location.

• Data redundancy occurs when different divisions, functional areas and groups in an organization independently collect the same pieces of information

• Data inconsistency: The same attribute may have different values.



• The coupling of data stored in files and the specific programs required to update and maintain those files such that changes in programs require changes to the data. For example, Tax rate.

Lack of flexibility:

• A traditional file system can deliver routine scheduled reports after extensive programming efforts, but it cannot deliver ad-hoc reports or respond to unanticipated information requirements in a timely fashion.


Program-data dependence:

Problems with the Traditional File Environment (Continued)


• Because there is little control or management of data, management will have no knowledge of who is accessing or even making changes to the organization’s data.

Lack of data sharing and availability:

• Information cannot flow freely across different functional areas or different parts of the organization. Users find different values of the same piece of information in two different systems, and hence they may not use these systems because they cannot trust the accuracy of the data.


Poor security:Problems with the Traditional File Environment (Continued)



Traditional File Processing

Figure 7-3


Database Management System (DBMS)

• DBMS is another software like word, excel or e-mail.

• It permits an organization to centralize data, manage them efficiently and provide access to the stored data by application program.

• Software for creating and maintaining databases • Permits firms to rationally manage data for the

entire firm • Acts as interface between application programs

and physical data files • Solves many problems of the traditional data file

approach

THE DATABASE APPROACH TO DATA MANAGEMENT


The Contemporary Database Environment


Figure 7-4


The Advantages of a DBMS

• Improved availabilityOne of the principle advantages of a DBMS is that the same information can be made available to different users.

• Minimized redundancy The data in a DBMS is more concise because, as a general rule, the information in it appears just once. This reduces data redundancy, or in other words, the need to repeat the same data over and over again. Minimizing redundancy can therefore significantly reduce the cost of storing information on hard drives and other storage devices. In contrast, data fields are commonly repeated in multiple files when a file management system is used.

• Accuracy: Accurate, consistent, and up-to-date data is a sign of data integrity. DBMSs foster data integrity because updates and changes to the data only have to be made in one place. The chances of making a mistake are higher if you are required to change the same data in several different places than if you only have to make the change in one place.



• Program and file consistency: Using a database management system, file formats and system programs are standardized. This makes the data files easier to maintain because the same rules and guidelines apply across all types of data. The level of consistency across files and programs also makes it easier to manage data when multiple programmers are involved.

• User-friendly: Data is easier to access and manipulate with a DBMS than without it. In most cases, DBMSs also reduce the reliance of individual users on computer specialists to meet their data needs.



• Improved security:

As stated earlier, DBMSs allow multiple users to access the same data resources. This capability is generally viewed as a benefit, but there are potential risks for the organization. Some sources of information should be protected or secured and only viewed by select individuals. Through the use of passwords, database management systems can be used to restrict data access to only those who should see it.


Commonly used database software

• Oracle

• SQL Server

• IBM DB2

• Sybase

• MS Access etc


Components of DBMS:

• Data definition language: Specifies content and structure of database and defines each data element. It involves in creating a common language.

• Data manipulation language: Formal language programmers used to process data in a database

• SQL is most prominent Data manipulation Language.

• Data dictionary: Stores definitions of data elements and data characteristics



Sample Data Dictionary Report


Figure 7-5


Types of Databases:

• Relational DBMS

• Hierarchical and network DBMS

• Object-oriented databases



Relational DBMS:

• Represents data as two-dimensional tables called relations

• Relates data across tables based on common data element

• Here each table contain a primary key, a unique identifier for each record. To make sure the tables relate to each other, the primary key from one table is stored in a related table as a secondary key.

• For example, in the customer table the primary key is “Customer ID”. That primary key is then stored in the order table as the secondary key so that two tables have a direct relationship.



The Relational Data Model


Figure 7-6


Three Basic Operations in a Relational Database:

• Select: Creates subset of rows that meet specific criteria

• Join: Combines relational tables to provide users with information

• Project: Enables users to create new tables containing only relevant information



The Three Basic Operations of a Relational DBMS


Figure 7-7


Hierarchical and Network DBMS Hierarchical and Network DBMS

• Organizes data in a tree-like structure• Supports one-to-many parent-child relationships

Think of a mother and her children. A child only has one mother and inherits some of her characteristics, such as eye color or hair color. A mother might have one or more children to whom she passes some of her characteristics but usually not exact ones. The child then goes on to develop her own characteristics separate from the mother.


Hierarchical DBMS:


In a hierarchical database, characteristics from the parent are passed to the child by a pointer, just as a human mother will have a genetic connection to each human child.


A Hierarchical Database for a Human Resources System


Figure 7-8



• Depicts data logically as many-to-many relationships


Network DBMS:


The Network Data Model

Figure 7-9


• Showing the relationship the students in a university have to courses they take.



• Outdated

• Less flexible compared to RDBMS

• Lack support for ad-hoc and English language-like queries

Disadvantages:



• Many companies are moving away from strictly text-based database systems. Data as objects can be pictures, groups of text, voice, and audio.

• Object-oriented DBMS: Stores data and procedures as objects that can be retrieved and shared automatically

• Object-relational DBMS: Provides capabilities of both object-oriented and relational DBMS

Object-Oriented Databases:



Data warehouse:

• Data warehousing is a huge computer files that store old and new data about anything and everything that a company wants to maintain information on.

• Supports reporting and query tools • Stores current and historical data • Consolidates data for management analysis and

decision making

DATABASE TRENDS

Data Warehousing and Data Mining Data Warehousing and Data Mining


Components of a Data Warehouse

DATABASE TRENDS

Figure 7-15


Data mining

On the other hand Data Mining is the tools for analyzing large pools of data. It can find hidden patterns and infer rules to predict trends. By using data mining, a digital firm can get more information than ever before from its data. Many companies collect lots of data about their business and customers. The most difficult part has been to turn that data into useful information. Firms are using better data mining techniques to target customers and suppliers with just the right information at the right time.


Applications of Data Mining

• By recording the activity of shoppers in an online store, such as Amazon.com, over time, retailers can use knowledge of these patterns to improve the placement of items in the layout of a mail-order catalog page or Web page.

• Telephone companies mine customer billing data to identify customers who spend considerably more than average on their monthly phone bill. The company can then target these customers to sell additional services.

• Marketers can effectively target the wants and needs of specific consumer groups by analyzing data about customer preferences and buying patterns.

• Hospitals use data mining to identify groups of people whose healthcare costs are likely to increase in the near future so that preventative steps can be taken.


Linking Internal Databases to the Web

DATABASE TRENDS

Figure 7-17


DATABASE TRENDSLinking Internal Databases to the Web

The benefits of using a Web browser to access a database are as follows:

• Ease-of-use. • Less training for users. • No changes to the internal database. • Cheaper than building a new system. • Creating new efficiencies and opportunities. • Provide employees with integrated firm wide views

of information.

7.1 © 2006 by Prentice Hall Managing Data Resources Md. Rashedul Hasan.

Documents

Transcript of 7.1 © 2006 by Prentice Hall Managing Data Resources Md. Rashedul Hasan.