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Management Management Information Systems, Information Systems,

10/e10/eRaymond McLeod and George Schell Raymond McLeod and George Schell

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Chapter 6Chapter 6Database Management Systems Database Management Systems

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Learning ObjectivesLearning Objectives

► Understand the hierarchy of data.Understand the hierarchy of data.► Understand database structures and how they Understand database structures and how they

work.work.► Know how to relate tables together in a database.Know how to relate tables together in a database.► Recognize the difference between a database and Recognize the difference between a database and

a database management system.a database management system.► Understand the database concept.Understand the database concept.► Know two basic methods for determining data Know two basic methods for determining data

needs.needs.

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Learning Objectives (Cont’d)Learning Objectives (Cont’d)

► Understand entity-relationship diagrams and class Understand entity-relationship diagrams and class diagrams.diagrams.

► Know the basics of reports and forms.Know the basics of reports and forms.► Understand the basic difference between Understand the basic difference between

structured query language and query-by-example.structured query language and query-by-example.► Know about the important personnel who are Know about the important personnel who are

associated with databases.associated with databases.► Know the advantages and costs of database Know the advantages and costs of database

management systems.management systems.

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Data HierarchyData Hierarchy

►Data fieldData field is the smallest unit of data. is the smallest unit of data.►RecordRecord is a collection of related data fields. is a collection of related data fields.►FileFile is a collection of related records. is a collection of related records.►DatabaseDatabase is a collection of related files. is a collection of related files.

General definitionGeneral definition Restrictive definitionRestrictive definition

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DatabaseDatabase► Table of rows & columns can be represented in a Table of rows & columns can be represented in a

spreadsheet.spreadsheet.► Relational database structureRelational database structure is conceptually is conceptually

similar to a collection of related tables.similar to a collection of related tables.► Flat f i leFlat f i le is a table that does not have repeating is a table that does not have repeating

columns; 1columns; 1stst normal form. normal form.► NormalizationNormalization is a formal process for eliminating is a formal process for eliminating

redundant data fields which preserving the ability redundant data fields which preserving the ability of the database to add, delete, and modify records of the database to add, delete, and modify records without causing errors.without causing errors.

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Figure 6.1 Spreadsheet as a Simple Figure 6.1 Spreadsheet as a Simple DatabaseDatabase

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Database (Cont’d)Database (Cont’d)

► KeyKey in a table is a field (or combination of fields) in a table is a field (or combination of fields) that contain a value that uniquely identifies each that contain a value that uniquely identifies each record in the table.record in the table.

► Candidate keyCandidate key is a field that uniquely identifies is a field that uniquely identifies each table row but is not the chosen key.each table row but is not the chosen key.

► Relating tables is done through sharing a common Relating tables is done through sharing a common field & the value of the field determines which rows field & the value of the field determines which rows in the tables are logically joined.in the tables are logically joined.

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Database Management SystemDatabase Management System

►Database management system Database management system (DBMS)(DBMS) is a software application that is a software application that stores the structure of the database, the stores the structure of the database, the data itself, relationships among data in the data itself, relationships among data in the database, and forms & reports pertaining to database, and forms & reports pertaining to the database.the database. Self-describing set of related data.Self-describing set of related data.

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Database StructuresDatabase Structures

►HierarchicalHierarchical is formed by data groups, is formed by data groups, subgroups, and further subgroups; like subgroups, and further subgroups; like branches on a tree.branches on a tree. Worked well with TPSs.Worked well with TPSs. Utilized computer resources efficiently.Utilized computer resources efficiently.

►NetworkNetwork allows retrieval of specific allows retrieval of specific records; allows a given record to point to records; allows a given record to point to any other record in the database.any other record in the database.

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Figure 6.2 Hierarchical StructureFigure 6.2 Hierarchical Structure

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Database Structures (Cont’d)Database Structures (Cont’d)

►RelationalRelational is when the relationship is when the relationship between tables are implicit.between tables are implicit.

►Physical relationshipPhysical relationship is when the is when the database structure (hierarchical, network) database structure (hierarchical, network) rely on storage addresses.rely on storage addresses.

► Implicit relationshipImplicit relationship is when the is when the database structure (relational) can be database structure (relational) can be implied from the data. implied from the data.

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A Relational Database ExampleA Relational Database Example►A database named A database named ScheduleSchedule has been created has been created

from tables used earlier in the chapter and some from tables used earlier in the chapter and some othersothers

►The database is implemented in Microsoft The database is implemented in Microsoft Access 2002 (also known as Access XP).Access 2002 (also known as Access XP).

►Databases break information into multiple tables Databases break information into multiple tables because if information were stored in a single because if information were stored in a single table, many data field values would be table, many data field values would be duplicated.duplicated.

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ScheduleSchedule Database Database► The example is implemented on Microsoft Access DBMS but The example is implemented on Microsoft Access DBMS but

would be similar on any relational DBMS product.would be similar on any relational DBMS product. ► The COURSE table in Access (Figure 6.4) is a list of data field The COURSE table in Access (Figure 6.4) is a list of data field

values. The table itself had to be defined in Access before values values. The table itself had to be defined in Access before values were entered into the data fields. were entered into the data fields.

► Figure 6.5 shows the definition of the Figure 6.5 shows the definition of the CodeCode field. field.► Figure 6.6 illustrates that Figure 6.6 illustrates that AbbreviationAbbreviation field values will be field values will be

looked up from a list of values in the DEPARTMENT table.looked up from a list of values in the DEPARTMENT table.► Table 6.7 shows a single table of course and department fields Table 6.7 shows a single table of course and department fields

before they were separated into different tables.before they were separated into different tables.

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Figure 6.4 The COURSE TableFigure 6.4 The COURSE Table

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Figure 6.5 Defining the CODE FieldFigure 6.5 Defining the CODE Field

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Figure 6.6 Look-up ValuesFigure 6.6 Look-up Values

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Table 6.7Table 6.7

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Figure 6.7 Access ViewFigure 6.7 Access View

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Database ConceptDatabase Concept

► Database conceptDatabase concept is the logical integration of is the logical integration of records across multiple physical locations.records across multiple physical locations.

► Data independenceData independence is the ability to make is the ability to make changes in the data structure without making changes in the data structure without making changes to the application programs that access changes to the application programs that access the data.the data.

► Data dictionaryData dictionary includes the definition of the includes the definition of the data stored within the database & controlled by the data stored within the database & controlled by the database management system.database management system.

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Creating a DatabaseCreating a Database

►Determine data that needs to be collected & Determine data that needs to be collected & stored is a key step.stored is a key step.

►Process-oriented approachProcess-oriented approach Define the problem.Define the problem. Identify necessary decisions.Identify necessary decisions. Describe information needs.Describe information needs. Determine the necessary processing.Determine the necessary processing. Specify data needs. Specify data needs.

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Determine Data Needs (Cont’d)Determine Data Needs (Cont’d)

►Enterprise modeling approachEnterprise modeling approach takes a takes a broad view of the firm’s data resources; all broad view of the firm’s data resources; all areas are considered, & synergy of data areas are considered, & synergy of data resources between business areas can be resources between business areas can be leveraged.leveraged. Result: Result: Enterprise data modelEnterprise data model

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Figure 6.8 Enterprise Data ModelFigure 6.8 Enterprise Data Model

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Data Modeling TechniquesData Modeling Techniques►Entity-relationship diagrams (ERDs)Entity-relationship diagrams (ERDs)

is a graphical representation of data in is a graphical representation of data in entities and the relationships between entities and the relationships between entities.entities.

►EntityEntity is a conceptual collection of related is a conceptual collection of related data fields.data fields.

►RelationshipRelationship is defined between entities. is defined between entities. One-to-one – 1:1One-to-one – 1:1 One-to-many – 1:MOne-to-many – 1:M Many-to-many – M:NMany-to-many – M:N

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Figure 6.11 Entity-relationship Figure 6.11 Entity-relationship DiagramDiagram

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Diagramming Techniques (Cont’d)Diagramming Techniques (Cont’d)

►Class DiagramClass Diagram is a graphical is a graphical representation of both the data used in an representation of both the data used in an application and the actions associated with application and the actions associated with the data; object-oriented design modelthe data; object-oriented design model

►ObjectsObjects are the data, actions taken on the are the data, actions taken on the data, & relationship between objects.data, & relationship between objects.

►Class diagrams consist of the named class, Class diagrams consist of the named class, fields in the class, & actions (fields in the class, & actions (methodsmethods) that ) that act upon the class.act upon the class.

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Figure 6.13 Class DiagramFigure 6.13 Class Diagram

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Using the DatabaseUsing the Database

►FormsForms show 1 record at a time & can be show 1 record at a time & can be used to add, delete, or modify database used to add, delete, or modify database records.records. NavigationNavigation AccuracyAccuracy ConsistencyConsistency FilteringFiltering subformssubforms

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Figure 6.15 Combined Data Entry Figure 6.15 Combined Data Entry FormForm

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Using the Database (Cont’d)Using the Database (Cont’d)

►ReportsReports are aggregated data from the are aggregated data from the database that are formatted in a manner database that are formatted in a manner that aids decision making.that aids decision making.

►QueriesQueries is a request for the database to is a request for the database to display selected records.display selected records.

►Query-by-example (QBE)Query-by-example (QBE) presents a presents a standardized form that the user completes standardized form that the user completes so the system can generate a true query.so the system can generate a true query.

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Figure 6.16 Report of DepartmentsFigure 6.16 Report of Departments

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Structured Query LanguageStructured Query Language

►Structured query language (SQL)Structured query language (SQL) is is the code that RDBMSs use to perform their the code that RDBMSs use to perform their database tasks.database tasks.

►Method of choice for interacting with web-Method of choice for interacting with web-based databases.based databases.

►Writing SQL statements are not difficult for Writing SQL statements are not difficult for most manager’s data needs.most manager’s data needs.

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Figure 6.20 SQL CodeFigure 6.20 SQL Code

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Advanced Database ProcessingAdvanced Database Processing

► On-line analytical processing (OLAP)On-line analytical processing (OLAP) allows allows data analysis similar to statistical cross-tabulation.data analysis similar to statistical cross-tabulation.

► Data miningData mining, , data martsdata marts, & , & data warehousingdata warehousing focus on methodologies that offer users quick focus on methodologies that offer users quick access to aggregated data specific to their access to aggregated data specific to their decision-making needs.decision-making needs.

► Knowledge discoveryKnowledge discovery analyzes data usage & analyzes data usage & data commonality among different tables.data commonality among different tables.

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Database PersonnelDatabase Personnel

►Database Administrator (DBA)Database Administrator (DBA) is an is an expert in developing, providing, and expert in developing, providing, and securing databases; duties includesecuring databases; duties include Database planning;Database planning; Database implementation;Database implementation; Database operation;Database operation; Database security.Database security.

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Database Personnel (Cont’d)Database Personnel (Cont’d)►Database programmerDatabase programmer writes code to writes code to

strip and/or aggregate data from the strip and/or aggregate data from the databasedatabase High level of specialization & selectionHigh level of specialization & selection

►End userEnd user generates reports & forms, post generates reports & forms, post queries to the database, & use results from queries to the database, & use results from their database inquiries to make decisions their database inquiries to make decisions that affect the firm & its environmental that affect the firm & its environmental constituents. constituents.

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DBMSs in PerspectiveDBMSs in Perspective►DBMS AdvantagesDBMS Advantages

Reduce data redundancy.Reduce data redundancy. Achieve data independence.Achieve data independence. Retrieve data & information rapidly.Retrieve data & information rapidly. Improve security.Improve security.

►DBMS DisadvantagesDBMS Disadvantages Obtain expensive software.Obtain expensive software. Obtain a large hardware configuration.Obtain a large hardware configuration. Hire and maintain a DBA staff.Hire and maintain a DBA staff.