McLeod_CH06.ppt 716KB Jan 27 2009 08:29:50 AM

Management
Information Systems,
Raymond McLeod
10/eand George
Schell

© 2007 by Prentice Hall

Management Information Systems, 10/e R
aymond McLeod and George Schell

1

Chapter 6
Database Management
Systems

© 2007 by Prentice Hall

Management Information Systems, 10/e R
aymond McLeod and George Schell

2

Learning Objectives
► Understand

the hierarchy of data.
► Understand database structures and how they
work.
► Know how to relate tables together in a
database.
► Recognize the difference between a database
and a database management system.
► Understand the database concept.
► Know two basic methods for determining data
needs.
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Learning Objectives (Cont’d)
► Understand

entity-relationship diagrams and
class diagrams.
► Know the basics of reports and forms.
► Understand the basic difference between
structured query language and query-byexample.
► Know about the important personnel who are
associated with databases.
► Know the advantages and costs of database
management systems.
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Data Hierarchy
► Data

field is the smallest unit of data.
► Record is a collection of related data
fields.
► File is a collection of related records.
► Database is a collection of related
files.
 General definition
 Restrictive definition
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Database
► Table

of rows & columns can be represented in a
spreadsheet.
► Relational database structure is conceptually
similar to a collection of related tables.
► Flat file is a table that does not have repeating
columns; 1st normal form.
► Normalization is a formal process for
eliminating redundant data fields which
preserving the ability of the database to add,
delete, and modify records without causing
errors.
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Figure 6.1 Spreadsheet as a
Simple Database

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Database (Cont’d)
► Key

in a table is a field (or combination of

fields) that contain a value that uniquely
identifies each record in the table.
► Candidate key is a field that uniquely
identifies each table row but is not the
chosen key.
► Relating tables is done through sharing a
common field & the value of the field
determines which rows in the tables are
logically joined.
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Database Management
System
► Database

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

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Database Structures
► Hierarchical

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

► Network

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

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Figure 6.2 Hierarchical
Structure

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Database Structures (Cont’d)
► Relational

is when the relationship
between tables are implicit.
► Physical relationship is when the
database structure (hierarchical,
network) rely on storage addresses.
► Implicit relationship is when the

database structure (relational) can be
implied from the data.
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A Relational Database
Example
► A database named Schedule

has been created
from tables used earlier in the chapter and some
others
► The database is implemented in Microsoft
Access 2002 (also known as Access XP).
► Databases break information into multiple tables

because if information were stored in a single
table, many data field values would be
duplicated.
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Schedule Database
►
►

►
►
►

The example is implemented on Microsoft Access DBMS but
would be similar on any relational DBMS product.
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
were entered into the data fields.
Figure 6.5 shows the definition of the Code field.
Figure 6.6 illustrates that Abbreviation field values will be
looked up from a list of values in the DEPARTMENT table.
Table 6.7 shows a single table of course and department fields
before they were separated into different tables.

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Figure 6.4 The COURSE Table

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Figure 6.5 Defining the CODE
Field

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Figure 6.6 Look-up Values

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Table 6.7

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Figure 6.7 Access View

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Database Concept
► Database

concept is the logical integration
of records across multiple physical locations.
► Data independence is the ability to make
changes in the data structure without making
changes to the application programs that
access the data.
► Data dictionary includes the definition of
the data stored within the database &
controlled by the database management
system.
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Creating a Database
► Determine

data that needs to be
collected & stored is a key step.
► Process-oriented approach






Define the problem.
Identify necessary decisions.
Describe information needs.
Determine the necessary processing.
Specify data needs.

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Determine Data Needs
(Cont’d)
► Enterprise

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

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Figure 6.8 Enterprise Data
Model

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Data Modeling Techniques
► Entity-relationship

diagrams (ERDs)
is a graphical representation of data in
entities and the relationships between
entities.
► Entity is a conceptual collection of
related data fields.
► Relationship is defined between entities.
 One-to-one – 1:1
 One-to-many – 1:M
 Many-to-many – M:N
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Figure 6.11 Entity-relationship
Diagram

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Diagramming Techniques
(Cont’d)
► Class

Diagram is a graphical
representation of both the data used in
an application and the actions associated
with the data; object-oriented design
model
► Objects are the data, actions taken on
the data, & relationship between objects.
► Class diagrams consist of the named
class, fields in the class, & actions
(methods) that act upon the class.
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Figure 6.13 Class Diagram

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Using the Database
► Forms

show 1 record at a time & can
be used to add, delete, or modify
database records.






Navigation
Accuracy
Consistency
Filtering
subforms

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Figure 6.15 Combined Data
Entry Form

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Using the Database (Cont’d)
► Reports

are aggregated data from the
database that are formatted in a manner
that aids decision making.
► Queries is a request for the database to
display selected records.
► Query-by-example (QBE) presents a
standardized form that the user
completes so the system can generate a
true query.
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Figure 6.16 Report of
Departments

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Structured Query Language
► Structured

query language (SQL)
is the code that RDBMSs use to
perform their database tasks.
► Method of choice for interacting with
web-based databases.
► Writing SQL statements are not
difficult for most manager’s data
needs.
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Figure 6.20 SQL Code

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Advanced Database
Processing
► On-line

analytical processing (OLAP)
allows data analysis similar to statistical
cross-tabulation.
► Data mining, data marts, & data
warehousing focus on methodologies that
offer users quick access to aggregated data
specific to their decision-making needs.
► Knowledge discovery analyzes data usage
& data commonality among different tables.
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Database Personnel
► Database

Administrator (DBA) is
an expert in developing, providing, and
securing databases; duties include





Database planning;
Database implementation;
Database operation;
Database security.

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Database Personnel (Cont’d)
► Database

programmer writes code
to strip and/or aggregate data from
the database
 High level of specialization & selection

► End

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

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DBMSs in Perspective
► DBMS






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

► DBMS





Advantages

Disadvantages

Obtain expensive software.
Obtain a large hardware configuration.
Hire and maintain a DBA staff.

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