Chapter 1 - testing

Chapter 1
Database and Database
Users
Dr. Bernard Chen Ph.D.
University of Central Arkansas

Outline
 Database Introduction
 An Example
 Characteristics of the Database
 Actors on the Scene
 Advantages of using the DBMS
approach

Database Examples
 Database is involved like everywhere in our
world
 For example:
If we go to bank to deposit or withdraw
Make hotel and airline reservation
Purchase something on line
Buy groceries in supermarkets

Database Applications
 These examples are what we called traditional
database applications
(First part of book focuses on traditional applications)
 More Recent Applications:
 Youtube
 iTunes
 Geographic Information Systems (GIS)
 Data Warehouses
 Many other applications

Database can be any size and
complexity
For example:
 A list of names and address
 IRS
(assume it has 100 million taxpayers and each
taxpayer file 5 forms with 400 characters of
information per form=800Gbyte)
 Amazon.com
(15 million people visit per day; about 100 people are
responsible for database update)

Database System
 Database:
A collection of related data.
 Data:
Known facts that can be recorded and have an
implicit meaning.
 Database Management System
(DBMS):
A software package/system to facilitate the
Define, Construct, Manipulate and Share functions
of a computerized database.

Typical DBMS Functionality
 Define a particular database in terms of its data types,
structures, and constraints
 Construct or Load the initial database contents on a secondary
storage medium
 Manipulate the database:
 Retrieval: Querying, generating reports
 Modification: Insertions, deletions and updates to its content
 Accessing the database through Web applications
 Share a database allows multiple users and programs to access
the database simultaneously

Database System
 Database System:
DBMS + Database

Simplified database system
environment

An UNIVERSITY example
 A UNIVERSITY database for maintaining information
concerning students, courses, and grades in a
university environment
 We have:
STUDENT file stores data on each student
COURSE file stores data on each course
SECTION file stores data on each section of each
course
GRADE_REPORT file stores the grades that students
receive
PREREQUISITE file stores the prerequisites

Database manipulation
 Database manipulation involves querying
and updating
 Examples of querying are:
Retrieve a transcript
List the prerequisites of the “Database” course
 Examples of updating are:
Enter a grade of “A” for “Smith” in “Database”
course

Database V.S. File
 In the database approach, a single repository of data
is maintained that is defined once then accessed by
various users
 The major differences between DB and File are:
1. Self-describing of a DB
2. Insulation between programs and data
3. Support of multiple views of the data
4. Sharing of data and multiuser transaction processing

Self-describing nature of a
database system
 Database system contains not only the
database itself but also a complete definition
of the database structure and constrains
 The information stored in the catalog is called
Meta-data (data about data), and it
describes the structure of the primary
database.

Example of a simplified Meta-
data

Insulation between programs
and data
 In file processing, if any changes to the
structure of a file may require changing all
programs that access the file
 In database system, the structure of data files
is stored in the DBMS catalog separately from
the access program
 This is called program-data
independence

Support of multiple views of
the data
 Each user may see a different view of
the database, which describes only the
data of interest to that user
 It may also contain some virtual data
that is derived from the database files
but its not explicitly stored

Sharing of data and multi-user
transaction processing
 Allowing a set of concurrent users to
retrieve from and to update the database.
 Concurrency control within the DBMS
guarantees that each transaction is
correctly executed or aborted
 For example, when several reservation clerks try
to assign a seat on an airplane flight
 (these types of applications are generally called
online transaction processing (OLTP))

Database Users
 Database administrators:
 Responsible for authorizing access to the database, for
coordinating and monitoring its use, acquiring software and
hardware resources, controlling its use and monitoring
efficiency of operations.
 Database Designers:
 Responsible to define the content, the structure, the
constraints, and functions or transactions against the
database. They must communicate with the end-users and
understand their needs.
 End Users
 System Analysts

End Users

Casual: access database occasionally by
sophisticated query language when needed.
(Manager)

Naïve: they make up a large section of the
end-user population. Learn only a few facilities
that they may use repeatedly
(bank clerk)

Sophisticated: These include business
analysts, scientists, engineers, others
thoroughly familiar with the system capabilities.

Stand-alone: maintain personal database by
using well designed GUI (Turbotax users)

Controlling Redundancy
 Controlling Redundancy is one of most
important feature to use DBMS
 The traditional file approach, each group
independently keeps their own file.
 For example: accounting office keeps data on
registration and billing info; whereas the
registration office keeps track of registration,
student courses and grades.

Controlling Redundancy
 This redundancy in storing the same data
multiple times leads to several problems:
1. Logic update – we need to update several
times
2. Storage space is wasted
3. The file that represent the same data may
become inconsistent

Other Advantages of using the
DBMS approach
 Restricting unauthorized access to data
 Providing Storage Structures (e.g.
indexes) for efficient Query Processing
 Providing backup and recovery services

Other Advantages of using the
DBMS approach
 Providing multiple interfaces to different
classes of users
 Representing complex relationships among
data
.
.
.

When NOT to use DBMS?
 The overhead cost of using DBMS:
 High initial investment in hardware,
software and training
 The cost of defining and processing data
 Overhead for security, concurrency control,
recovery, and integrity functions

When NOT to use DBMS?
 Hence, it may be more desirable to use
regular files under the following
situations:
 Simple, well-defined database applications
that are not expected to change
 Real-time requirements for some programs
that may not be met due to DBMS
overheads
 No multiple-user access to data

Chapter 1 - testing

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Chapter 1 - testing