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The University of Akron
Dept of Business Technology
Computer Information Systems
2440: 180
Database Concepts
Instructor: Enoch E. Damson
Intro to Database Management
File Processing Systems

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Developed to store, manipulate, and retrieve
large files of data in the early stages of the
introduction of computers into the business
world
In the file processing environment:


Files are used to store data in organizations
Each user area has its own collection of files
independent of other files
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File Processing Keywords
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Byte (character) - a group of bits (8 bits)
Field – a collection of characters
Record – a collection of fields
File – a collection of records
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Disadvantages of File Processing
Systems

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Program-Data Dependence – changes to a file
structure requires changes to file descriptions for
programs that access the file
Data Redundancy – duplicate data files often:
 Wastes space
 Makes updates cumbersome and time-consuming
 Lead to data inconsistencies
 Result in loss of data integrity
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Disadvantages of File Processing
Systems…
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Limited Data Sharing – each application has its own
private files which limits data sharing
Poor Programmer Productivity – new applications
require the developer to start designing from scratch
Excessive Program Maintenance – heavy program
maintenance loads are created based on the
disadvantages above
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Database Processing
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Emphasizes the integration and sharing of data
throughout an organization
The term database system refers to an organization of
components that define and regulate the collection,
storage, management, and use of data within a database
environment

A database system is simply a database and a database
management system (DBMS) put together
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What is a Database?

An organized collection of data (and
metadata) about the activities of entities
and the relationships among these entities
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Database Definition Keywords

Data – raw facts

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Information – processed data
Metadata – data that describe the properties of
other data

The properties include:
 Data
definitions
 Data structures
 Rules or constraints
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Database Definition Keywords…

Entity – a person, thing, place, or event for
which data is collected
May also be known as a relation, table or file
 E.g., customer, orders etc could be entities in a
database
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Attribute – a property of an entity
May also be termed a field or a column
 E.g., a customer entity may have name, address etc
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Relationship – association between entities
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Types of Entity Relationships
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One-to-many relationships
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Many-to-many relationships
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E.g., each department has many employees but each
employee belongs to only one department
E.g., each student can take many courses and each course
could be taken by many students
One-to-one relationships

E.g., each team is managed by a coach and a coach
manages a single team
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Entities & Attributes
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Entity Relationship

One-to-many
relationship
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Records
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A collection of fields
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May also be termed a row or a tuple
Below is are examples of two entities with records
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Other Database Definitions

A database is:

Self-describing (metadata) – does not rely on a
separate structure for information (logically
complete)
 Integrated (Related) – contains relationships
among entities
 Shared – more than one user has access to the data
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Entity-Relationship Diagram
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
Visual representation of a database
Various versions of entity-relationship diagrams
exist
Rectangles represent entities
 Lines represent relationships between connected
entities
 Other forms have circles representing attributes

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Entity-Relationship Diagram…
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Database Management System
(DBMS)
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Software that manages a database

Three basic functions include:

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
Defining a database – specifying the metadata (data
types, constraints, etc) for data storage
Constructing a database – storing data
Manipulating a database – querying the database for
specific data, updating the database and generating
reports from the data
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Types of DBMSs
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Popular DBMSs include:

Access (by Microsoft)
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Oracle (by Oracle)
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DB2 (by IBM)
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SQL Server (by Microsoft)
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MySQL

dBASE

Paradox

Informix
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Different DBMS Usage

Using a DBMS
directly

Using a DBMS
through another
program
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Components of a DBMS
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A DBMS is evaluated based on the:
Database engine
 Data dictionary
 Query processor
 Report writer
 Forms generator
 Communication & integration utilities
 Security utilities

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Components of a DBMS…

Database engine – responsible for storing,
retrieving, and updating the data
 Data dictionary – holds the metadata of the
data tables
 Query processor – allows users to store and
retrieve data with the use of a query language
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Components of a DBMS…

Report writer – generates database reports

Forms generator – helps to create input forms

for tasks such as data entry
Application generator – has tools (menus,
toolbar generators, etc) to assist the developer in
creating a complete application
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Components of a DBMS…

Communication and integration utilities –
help data storage and usage on different machines,
from different locations


E.g., modern operating systems and independent networks,
including the Internet, have made it easier to connect
databases running from different locations
Security utilities – establish and maintain
security access controls
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DBMS Data Models
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A DBMS allows users to define the data to be
stored in terms of a data model
Data model – a collection of high-level data
description constructs that hide many low-level
storage details

Has 2 components:
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Structure – the way systems structure data
Operations – facilities given to a DBMS user to
manipulate data within a database
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Types of Data Models
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Hierarchical model
Network model
Relational model
Object-Oriented model
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The Hierarchical Model
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Has a collection of records (hierarchies) perceived as organized
to conform to a top-down tree structure
The structure is perceived logically rather than physically
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Top layer is perceived as the parent of the segment directly beneath it
A segment beneath another segment is a child segment
Relatively fast approach (as long as data is accessed from top to bottom)
Can provide some difficulties in data search, especially items in the
bottom or middle of the hierarchy
Some hierarchical DBMSs include: Generalized Update Access
method (GUAM), Information Management System (IMS),
DL/I, Integrated Data Store (IDS), IDMS
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The Network Model
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Similar to the hierarchical model

Primary goal was to address the need to:
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Represent complex data relationships more effectively than the
hierarchical model
Improve on database performance
Impose database standards
Perceived as a collection of data sets
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Each set is composed of at least two record types:
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owner record (equivalent to the hierarchical model’s parent)
member record (equivalent to the hierarchical model’s child)
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The Relational Model
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E. F. Codd of IBM originated the relational model
approach in the 1970s
Has been the predominant method for data storage
The central data description construct is a table
(called “relation” by Dr. Codd)
Relation (entity) - a set of records, with the same
number and type of fields
Some relational DBMSs include: DB2, Oracle, Sybase,
Paradox, dBASE, Access, MySQL, SQL Server
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The Object-Oriented Model

Relatively new and evolving method of
organizing data
The goal of the model is to define objects that can
be reused in many programs, to save time and
reduce errors
 The objects have:

Properties (or attributes)
 Methods (or functions)
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Some Object-Oriented DBMSs include:
Gemstone, Objectivity/DB, Versant
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Types of Database Systems
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The DBMS, on which the database system is
based, can be classified according to the:
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Number of users
Site location
Type and extent of use
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Database System Types Based on
Number of Users
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Single-user database system – supports only
one user at a time
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E.g. Desktop Databases
Multi-user database system – supports
multiple users at the same time

E.g.
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Workgroup databases
Department databases
Enterprise databases
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Database System Types Based on
Number of Users…
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Desktop Databases – single-user databases that run on a
personal computer
Workgroup Databases – multi-user databases that support a
relatively small number of users (usually less than 25 users)
 Each member of the workgroup has a desktop computer and
the computers are linked by means of a local area network
(LAN)
 The database is stored on a central device called the database
server, connected to the network to make each group member
obtain access to the shared data
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Database System Types Based on
Number of Users…
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
Department Databases – similar to workgroup databases but
with a little larger number of group members (typically between
25 and 100 members) and responsible for a more diverse range
of functions
Enterprise Databases – multi-user databases with its scope on
the entire organization or enterprise
 Arguably, the most important type of enterprise database today
is called a data warehouse
 Data warehouse – an integrated decision support database
with content derived from various operational databases
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Database System Types Based on
Site Location
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Centralized database system – supports a

database located at a single site
Distributed database system – supports a
database distributed across several different sites
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Database System Types Based on
Extent of Usage


Transactional (production) database system –
supports “immediate response” transactions like
product or service sales, payments, etc
Decision support database system – focuses on
the production of information required for
tactical or strategic decisions such as sales
forecasting, pricing, market positioning, etc
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Other Database Systems

The past few years have produced advances in
technology leading to exciting new applications
of database systems such as:
Multimedia databases
 Geographic information systems
 Data warehouses

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Other Database Systems…

Multimedia databases – store pictures, video clips,
and sound messages

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Geographic information systems (GIS) – store and
analyze maps, weather data, and satellite images
Data warehouses and on-line analytical processing
(OLAP) or on-line transaction processing (OLTP)
systems – used to extract and analyze useful
information from very large databases for decisionmaking
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Advantages of Database
Processing
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Economy of Scale - cost of several combined
operations becomes less than the cost of individual
operations
More Information from Same Data - users are able
to acquire additional information from a pool of data
Shared Data - several users can gain access to the
same data
Balanced Conflicting Requirements - Database
Administrators structure databases to benefit a group
of users, rather than individual users in an
organization
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Advantages of Database
Processing…

Enforcement of Standards - DBAs set
standards for data access and usage
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E.g., illegal data retrieval
Controlled Redundancy - Databases are
structured to control redundancies
Data Consistency - Controlled redundancies
ensures data consistency
Data Integrity - Integrity constraints ensure
data integrity
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Advantages of Database
Processing…
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Data Security - unauthorized users can be
prevented from database access
Flexibility and Responsiveness - requests
from multiple users or areas are granted in an
efficient, effective, and flexible manner by
DBMSs
Increased Programmer Productivity - 4GLs
have cut down the time spent by programmers
and increased production enormously
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Advantages of Database
Processing…
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
Improved Program Maintenance - changes to
existing data structures might not need maintenance to
existing programs since programs are independent of
the structure of a database
Data Independence - the structure of a database can
change without requiring the application programs to
change

The structure of the database is independent from
application programs
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Disadvantages of Database
Processing

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
Size - DBMSs tend to occupy more disk space
and memory
Complexity - the several functions offered by a
DBMS can make it a complex product for
programmers to familiarize with
Cost - some DBMSs are very expensive (esp.
client/server DBMSs)
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Disadvantages of Database
Processing…
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
Additional Hardware Requirement - hardware
resources are required for multi-user DBMSs
Higher Impact of a Failure - failure in a DBMS
component can affect several users and other
components of the DBMS
Difficulty in Data Recovery - with the size and
complexity of a database, recovery becomes difficult in
case of data loss
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