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C
Accounting, Information Technology,
and Business Solutions, 2nd Edition
By Hollander, Denna, Cherrington
Date and Database Management Systems (DBMS)
PowerPoint slides by:
Bruce W. MacLean,
Faculty of Management,
Dalhousie University
Supplement C
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
Sample Flat File - Student
Physics 101
Last Name, First name
Assignments
ID #
Email
Major
Year #1
Einstein, Albert
123456
Bigal
Phys
1
9
2
Copernicus
234567
Coper
Math
3
5
5
Galileo
345678
Gali
Art
2
3
7
Hawking, Stephen
456789
HSteve
CS
4
8
4
Calvin
567891
Hobbes
Phys
5
10
10
Irwin/McGraw-Hill
#2
#3
#4 #5
The McGraw-Hill Companies, Inc., 2000
Supplement C: Objectives
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Describe the difference between file-oriented and
database environments.
Describe what a DBMS is.
Identify various types of DBMS software.
Describe common features of a DBMS.
Describe how DBMSs are used.
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
File Versus Database Environments
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Computer processing involves two components: data and
instructions (programs).
Conceptually, there are two methods for designing the interface
between program instructions and data.
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File-oriented processing A specific data file was created for each
application.
Data-oriented processing. Create a single data repository to support
numerous applications.
Disadvantages of file-oriented processing include redundant data
and programs and varying formats for storing the redundant
data.
The format for similar fields may vary because the programmer
used inconsistent field formats.
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
Comparison of File Structures
File Oriented
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Data Oriented
Mailing list: Customer
 Customer items: Customer
Number, Customer Name,
Number, Customer Name,
Customer Address . . .
and Customer Address.
Order file: Order Number,
 Order items: Order Date,
Date, Customer Number,
Order Number, Inventory
Customer Name, Customer
Ordered, Quantities Ordered,
Address, Inventory Items
and Customer Number.
Ordered, Quantities Ordered . .
 Shipment items: Shipment
Shipment file: Date, Shipment
Number, Order Number,
Date, Shipment Number,
Customer Number, Customer
Order Number, Customer
Name, Customer Address,
Number, Items Shipped, and
Inventory Items Ordered, Items
Balance Due for Shipment.
Shipped . . .
Redundant Items in Yellow
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
What is a Database Management
System (DBMS)
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A DBMS is the resource available to define and manage data
structures in an information system.
DBMS software was originally developed to simplify and
enhance the value of an organization’s data by reducing data and
programming redundancy, inconsistent data formats, and data
inconsistencies.
A DBMS environment allows the development and maintenance
of a data repository that is independent from application
programs.
Such flexibility enables database users to create and maintain IT
applications that capture, maintain, and report data while
shielding application developers from the physical structure and
maintenance of the data repository.
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
Types of DBMS Software
Tree or hierarchical
Network
Relational
Object oriented
Application A
Data
Irwin/McGraw-Hill
DBMS
Application B
The McGraw-Hill Companies, Inc., 2000
Hierarchical Logical Structures
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Hierarchical databases (also called tree databases) organize and
search data using the structure of a family tree.
Each record of the hierarchical structure may have multiple
“child” records that are subordinate to it. See next Slide
Choosing which records are superior and which records are
subordinate depends in part on storage efficiency as well as on the
quantity and types of queries you anticipate.
Because the hierarchical structure can model only 1:1 and 1:*
maximum cardinalities, this restricts the usefulness of the
hierarchical database structure.
Hierarchical structures are commonly used to organize accounting
data when a chart of account structure is used.
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
Sample Tree Structure
COURSE RECORD
Course
Section
Teacher
Room
Time
Acc
1
Calvin
340
MW 1pm
First Name
Bob
Major
History
Grade
B
STUDENT
Student #
12345
RECORD
Last Name
Smith
23456
Sanders
Shelly
Math
A
34567
Samson
Jennifer
CS
C
COURSE RECORD
CS
1
Hobbes
205
Student
Record
TTh 2pm
12345
45678
Smith
Fisher
Bob
Mary
History
CS
B
A-
56789
Lincoln
Perry
Math
A
Irwin/McGraw-Hill
Course
Record
The McGraw-Hill Companies, Inc., 2000
Accounting Data in a Tree Structure
FINANCIAL STATEMENTS
Assets
Liabilities
Equity
Current Assets
Current Liabilities
Revenue
Property, Plant,
and Equipement
Long-term Liabilities
Expenses
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
Network Logical Structure
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The network structure allows any number of superior
records to be related to any number of subordinates
(and vice versa).
The distinction between parent and child records is
eliminated.
Using a network structure, Student records could be
subordinate to Course, and Course records could be
subordinate to Student records at the same time.
Network DBMS software is fairly complex because
you must know the physical structure of the data to be
able to search the database.
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
Relational Logical Structure
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Relational databases organize and store data in two-dimensional
tables consisting of rows and columns.
The table is arranged in columns, which are called attributes, or
domains, and rows, which are called records or tuples.
Each row of information in a table is called an instance.
One of the table fields is a unique identifier field (the key
attribute or primary key). Normally, each table contains:
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Data items about a particular group of people, resources, locations, or
business activity type.
– Putting only data items about a particular entity of object into a data table is
known as normalization. A table is in normal form if it only contains items
that describe the main theme or focus of the table (e.g., customers, sales
orders, or inventory) plus any fields needed to link the table with other tables.
– Data items (usually key attributes) that are used to combine or link tables.
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
Advantages of the Relational
Approach
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The relational approach to designing
databases allows more flexibility.
By introducing some limited
duplication into the data pool, users
are able to create relationships and
logical structures ad hoc, rather than
having to predefine relationships as
the database is created.
A change in the database does not
require rewriting all the application
program codes.
Like the network model, relational
databases can incorporate all of the
types of maximum relationship
cardinalities.
Irwin/McGraw-Hill
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Rather than physically linking data,
relational models make use of
logical tables to model structures.
Relationships among tables are
represented by common data values
in the tables.
The power of relational DBMS
software is the ability to maintain
several tables of related information
that can be accessed by several
different information customers in
many different ways
One of the great advantages of the
relational structure is its ability to
simplify the organization of
complex sets of data.
The McGraw-Hill Companies, Inc., 2000
Object Oriented Structure
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Objects contain both data as well
as methods (i.e., instructions for
processing the data).
The major advantage of object
oriented (OO) structures is their
increased flexibility to represent
very complex data structures that
capture the essence of complex
objects existing in reality.
Using object technology,
programmers can model and
implement complex data types
such as voice, video, audio, etc.
Irwin/McGraw-Hill
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Although OO has several
conceptual advantages over the
other structures, it is much
more computationally
demanding than even the pure
relational structure.
Today, there are a limited
number of pure object oriented
database applications in use.
However, as technology
improves, the frequency of
object oriented applications
will increase.
The McGraw-Hill Companies, Inc., 2000
Other Features of a DBMS
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Data Definition Commands which
are used to set up the data structures
and define user data views of the
data—these are known as logical
views or schemas;
Data Manipulation Commands which
are used to add, delete, and update
data in the structures;
Forms Generators which are used to
design the format and look of desired
screens and forms
Report Generators that are used to
define the format and look of desired
output.
DBMS environments provide
management and security features.
Irwin/McGraw-Hill
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Data Query Commands which
help users ask questions about
the data;
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Popular data query tools include
QBE (query by example) and SQL
(structured query language). Using
QBE, a grid or replica of an empty
record is displayed and the user
types search criteria in the
applicable columns.
SQL, on the other hand, is an actual
program language that you can use
to directly interact with data, or you
can embed SQL commands in
programs that access and process
data.; and
The McGraw-Hill Companies, Inc., 2000
DBMS (and File) Documentation
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The database generally consists of many files and each file
contains many records.
Each event represents one record.
Within each record there are many fields of data called data
items, with each data item representing one attribute about the
entity.
A record layout details the record structure, including record
field names, the width of each field, and the type of data stored
in each field (e.g., numeric, alphanumeric, or date).
Since database data items are shared by numerous applications,
database documentation, called data dictionaries, document data
item, rather than record level detail.
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
File Structure Relationships
File
Database
Record #1
Record #2
Record #3
Fields
Record Layout
Sale #
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Register #
Customer #
Employee #
The McGraw-Hill Companies, Inc., 2000
DBMS Analysis and Design
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Much of the work to develop a database and the
programs associated with it is completed during the
analysis, planning, and design stages of a system.
A central objective in analyzing and designing the
database is to identify the set of data needed to
document business activities (e.g., financing, selling,
purchasing, or marketing) and provide information
about parties (e.g., customers, vendors, or employees)
and resources (e.g., cash, services, or inventory)
involved in the business activities.
Irwin/McGraw-Hill
The McGraw-Hill Companies, Inc., 2000
DBMS Analysis and Design
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Architecture plans include an
overview of such DBMS
components as:
the specific data items and
structures needed,
the attributes of each data item,
the primary identifier for each
data structure,
a method for linking related data
items and structures (which
requires an understanding of
data/object relationships),
Irwin/McGraw-Hill
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needed business and
information controls,
needed help screens and
help functions,
input/output screens, report
formats, queries, and
documents, and
computer instructions
needed to perform
recording, maintenance,
and reporting tasks.
The McGraw-Hill Companies, Inc., 2000
Data Warehouses
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Data warehouses contain data
from operational databases, as
well as data from external sources.
The objective is to capture and
make available the knowledge and
information critical for analysis
and decision making
The data are combined and
duplicate, invalid, and unneeded
data is removed.
The data are aggregated (i.e.,
summarized) and organized by
dimension and/or subject area.
Irwin/McGraw-Hill
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Data warehouses provide
summary data as of a
certain point in time.
Data warehouse users can
mine the data and “slice
and dice” it to generate
desired outputs.
Users are sending a signal
that they need enterprisewide information views of
an organization to support
all levels of analysis and
decision making.
The McGraw-Hill Companies, Inc., 2000
Features of DBMS Software
Data Definition Commands
used to set up the data
structures and define user
data views -- known as
logical views or schemes
Security features
Forms Generators
used to design the
format and look of
desired screens and
forms
Report Generators
used to define the
format and look of
desired output.
Data Manipulation Commands
used to add, delete, and update
data in the structures
Data Query Commands
help users ask questions
about the data