Transcript Database Concepts Dr. Awad Khalil Computer Science Department AUC

Database Concepts
Dr. Awad Khalil
Computer Science Department
AUC
CSCI 253 -- Database Concepts
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Content

What and Why Database?

Database System Environment
The Database
 The Database Management System
 The Application Programs
 The Users


Characteristics of the Database approach
versus the Traditional File Approach
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What is a Database?

Databases are considered as major components in almost all
recent computer application systems, including business,
management, engineering, education, medicine, science, ... etc.
Database technology has a major impact on the growing use of
computer systems.

A database is simply a collection of related data.

Data mean known facts that can be recorded and that have
implicit meaning.


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Database Properties
database is a logically coherent collection of data
with some inherent meaning. A random collection of
data cannot be considered as a database.
A
database represents aspects of a real system in real
world. Examples of these real systems:
A
Hospital, Bank, Factory, Company, University, …
A
database is designed and implemented to afford the
informational needs of a specific group of users.
These informational needs are supported by a set of
application systems running against the implemented
database.
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Database – Example I
 Consider
a small personal database to maintain data
concerning
the names, telephone numbers, and
addresses of the people you know
TELEPHONE DIRECTORY
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Example II

Consider a suppliersand-parts database to
maintain
data
concerning suppliers
supplying parts for a
certain company.
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2
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Database Management System (DBMS) is a gene
purpose software that enables users to create and maintai
database. The DBMS facilitates the process of defin
constructing, and manipulating databases for var
applications.
T
h


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
e
De
f inin
g : Data Def initionL ang uag e( DD
L ).
Constructin
g .
Manipulatin
g : DataM anipulationL ang uag e( D
M L).
DBMSL ayers:
 Soft w
are to process Q ueries and P
rograms: ( DM
L ).
language SQ L( StructuredQ ueryL anguage
) is a typ
example of a database query language.
3- The Application Programs

Th es e ar e th e pro
g ram swr itten to s uppor t th e end us ers r eq uir em ents . A
g iv en end us er c an acc ess th e d atab as e v ia one of th eonline application s,
wh er e h e or sh e oper ates by ch oos ing item sf rom am enu orf illing in item s
on af orm . S uc h menu- orf o
rm s-driven interf ace stend to b e eas ier to us e
for people who do not have af ormal trainin
g in data processin
g .
Personnel
Application
Personnel
users
Common
Database
Payroll
Application
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Payroll
users
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4- Users
Database
Users
Professional
Users
Database
Designers
Database
Adnibistrators
End Users
System Analysts
& Application
Programmers
Casual
end users
Parametric
end users
CSCI 253 -- Database Concepts
Sophisticated
end users
Stand-alone
end users
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Characteristics of the Database Approach
 Self-describing
 Program-data
nature of a database
independence
and
Data
Abstraction
 Support
multiple views of the data
 Sharing
of data and multiuser transaction
processing
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Database Approach versus the Traditional File Approach
Personnel
files
Personnel
Application
Personnel
users
Personnel
Application
Personnel
users
Common
Database
Payroll
files
Payroll
Application
Payroll
users
Payroll
Application
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Payroll
users
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The Traditional File Approach

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1. Disadvantages:
Inflexibility: a “mass production facilty”
– committed to processing particular
queries.
Uncontrolled Redundancy: If these
separate applications need to process the
same data then must duplicate copies of
the data i.e., each application has its own
data files, several copies of the same data
may exist in different applications. This
leads to:

Wastage of valuable storage space.
 Need to input data to several files.

Data inconsistency (one fact may have more
than one value – various versions may occur).

Limited Data Sharing: Each
application has its own private file
providing little opportunity for
users to share existing data.
Additionally any new applications
would not be able to use existing
files leading to low productivity.

Progran – Data Dependency:
Descriptions of files, records, data
items
are
embedded
within
application
programs.
Any
modification to a data file requires
that the application programs using
that file must also be changed. In
other words, program maintenance
will be excessive.
Poor Enforcement of System Standards:
Data names, formats, access restrictions,
… etc. are not standardized across an
organization, may have many synonyms
and
homonyms.
This
makes
modifications difficult and hinders
sharing of data.
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The Database Approach

Th e d atab as e appr oach im pr ov es uponf ile-b as ed sys tem s . A D
M S
B
d oes notf rag m ent d ata int o s epar atef iles b ut r eg ards dat a as b eing
s tor ed in a larg e c onc ept ual r epos it ory ter m ed as database . Th e
DB
M
Sh and les th e add ition, s tor ag e, upd at e, and r etr iev al of data.
DB
M
Ss ar e b as ed on s em antic ally r ic h d ata m od els, wh ic h c an
accurately represent real world data. DB
M Ss allow:

Persistence o
f Data

Transaction Control

Concurrency Control

Recovery Control

Queryin
g

Integ rity Control

Data Security

Version Control

Perf ormance Tuning
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Components of DBMS

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DBMS Engine
Interface Subsystem( DDL, DML, DCL, Graphical User
Interface, Forms Interface, Natural Language Interface
System Catalog
Performance Management Subsystem
Data Integrity Management Subsystem
Backup and Recovery Subsystem
Application Development Subsystem
Security Management Subsystem
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Benefits of the Database Approach
 Ease
of application development
 Minimal data redundancy
 Enforcement of standards
 Data can be shared
 Physical data independence
 Logical data independence
 Better modeling of real world data
 Uniform security and integrity controls
 Economy of scale
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Thank you
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