Chapter 1
Databases and
Database Users
Prepared By
Dr. Alaa Hosni
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⚫Activities that involve some interaction with a
database (traditional database applications).
– deposit or withdraw funds,
– hotel or airline reservation,
– computerized library to search for a bibliographic
item
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⚫ In the past few years, advances in technology have
led to new applications of database systems.
⚫ New media technology has made it possible to store
– images,
– audio clips, and
– video streams digitally.
⚫ These types of files are becoming an important
component of multimedia databases.
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Examples
⚫ Geographic information systems (GIS) can
store and analyze maps, weather data, and
satellite images.
⚫ Real-time and active database technology is
used to control industrial and manufacturing
processes.
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1. Introduction
⚫ Database: A collection of related data.
⚫ Data: Known facts that can be recorded.
⚫ For example, consider the names, telephone
numbers, and addresses of the people you know.
⚫ Mini-world: Some part of the real world about
which data is stored in a database.
For example, student grades and transcripts at a
university.
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• Database Management System (DBMS): A
general-purpose software system to facilitate the
creation and maintenance of a computerized
database.
• Database System: DBMS + data
• Sometimes, the applications are also included.
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Example
Large commercial database is Amazon.com. It contains
data for over 20 million books, CDs, videos, DVDs,
games, … and other items.
• The database is stored on 200 different computers
(called servers).
• 1 TB = 1000 gigabytes terabytes (a terabyte is 1012
bytes worth of storage).
• More than 160 million visitors access Amazon.com
monthly.
• About 100 people are responsible for keeping the
Amazon database up-to-date.
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• Defining a database involves specifying
1. the data types,
2. structures, and
3. constraints of the data to be stored in the database.
• The database definition or descriptive information is
also stored by the DBMS in the form of a database
catalog or dictionary; it is called meta-data.
• Constructing the database is the process of storing
the data on some storage medium that is controlled by
the DBMS.
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• Manipulating a database includes :
1. querying the database to retrieve specific data,
2. updating the database to reflect changes in the miniworld, and
3. generating reports (is the formatted result of database queries
and contains useful data for decision-making and analysis. )
from the data.
• Sharing a database allows multiple users and programs
to access the database simultaneously.
• A transaction may cause some data to be read
and some data to be written into the database.
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Other features:
– Protection or Security measures to prevent
unauthorized access
– Presentation and Visualization of data
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2. An Example
• The UNIVERSITY database for maintaining
information concerning students, courses, and grades in a
university environment.
• The database is organized as five files, each of which
stores data records of the same type.
– The STUDENT file stores data on each student,
– The COURSE file stores data on each course,
– The SECTION file stores data on each section of a course,
– The GRADE_REPORT file stores the grades that students
receive in the various sections, and
– The PREREQUISITE file
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• Examples of queries are as follows:
– Retrieve the transcript—a list of all courses and
grades—of ‘Smith’
– List the names of students who took the section
of the ‘Database’ course offered in fall 2008
and their grades in that section
– List the prerequisites of the ‘Database’ course
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• Examples of updates include the following:
▪ Change the class of ‘Smith’
▪ Create a new section for the ‘Database’ course for
this semester
• Enter a grade of ‘A’ for ‘Smith’ in the ‘Database’
section of last semester
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• Design of a new application for an existing database or
design of a brand new database starts off with a phase called
requirements specification and analysis.
• These requirements are transformed into a conceptual
design.
• Conceptual Design is an early phase of the design process,
in which the broad outlines of function and form of
something are articulated.
• The conceptual design can be represented using some
computerized tools so that it can be transformed into a
database implementation.
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• The design is then translated to a logical design that
can be expressed in a data model implemented in a
commercial DBMS.
• Data model : Relational Data Model
• The final stage is physical design:further specifications
are provided for storing and accessing the database.
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Conceptual design (ER)
Logical design (data model)
Physical design (implementation)
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3. Characteristics of the Database Approach
⚫ Differences between the database approach and the
approach of programming with files.
– In file processing, each user defines and implements the
files needed for a specific software application.
– For example, one user, may keep files on students and their
grades. A second user, the, may keep track of students’ fees
and their payments.
⚫ This redundancy in defining and storing data results in
wasted storage space and in redundant efforts to
maintain common up-to-date data.
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⚫ The main characteristics of the database approach versus
the file-processing approach are the following:
1. Self-describing nature of a database system.
2. The database system contains in the DBMS catalog :
definition of the database structure and constraints.
3. Insulation between programs and data. The structure of data
files is stored in the DBMS catalog separately from the
access programs ( program-data independence).
4. Support of multiple views of the data
5. Sharing of data and multiuser transaction processing
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⚫ 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.
⚫ For example, one user of the university database
may be interested only in accessing and printing the
transcript of each student; the view for this user is
shown in Figure 1.5(a).
⚫ A second user: checking that students have taken all
the prerequisites of each course for which they
register, may require the view shown in Figure
1.5(b).
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Actors on the scene
– Database administrators: responsible for authorizing
access to the database, for co-ordinating and monitoring
its use, acquiring software, and hardware resources,
controlling its use.
– Database Designers: responsible to define the content,
the structure, the constraints, and functions or
transactions against the database.
– End-users: they use the data for queries, reports and
some of them actually update the database content.
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4. Advantages of Using the Database Approach
⚫ Controlling redundancy in data storage and in
development and maintenance efforts.
⚫ Sharing of data among multiple users.
⚫ Restricting unauthorized access to data.
⚫ Providing persistent storage for program Objects
– Object-oriented database systems are compatible with
programming languages such as C++ and Java, and the DBMS
software automatically performs any necessary conversions.
⚫ Providing Storage Structures for efficient Query
Processing
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⚫ Providing backup and recovery services.
⚫ Providing multiple interfaces to different classes
of users.
⚫ Representing complex relationships among data.
⚫ Integrity constraints on the database: every section
record must be related to a course record.
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