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Lecture1: Principles of Databases
Ref. Chapter1
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Prepared by L. Nouf Almujally
• Problems with file-based approach
• Meaning of the term database.
• Meaning of the term Database Management System
(DBMS).
• Major components of the DBMS environment.
• Users involved in the DBMS environment.
• Advantages and disadvantages of DBMSs.
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Chapter1 - Objectives
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File-Based Systems
• Collection of application programs that perform
services for the end users (e.g. reports).
• Each program defines and manages its own data.
Limitations of File-Based Approach
• Separation and isolation of data
• Each program maintains its own set of data.
• Users of one program may be unaware of
potentially useful data held by other programs.
• Duplication of data
• Same data is held by different programs.
• Wasted space and potentially different values
and/or different formats for the same item.
Limitations of File-Based Approach
• Data dependence
• File structure is defined in the program code.
• Definition of data was embedded in application
programs, rather than being stored separately and
independently.
• Incompatible file formats
• Programs are written in different languages, and
so cannot easily access each other’s files.
Pearson Education © 2009
DATABASE APPROACH
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Solution …
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Data
• facts about entities
• Person's name, Phone, address, email, picture, …
• Student's ID, name, subjects taken, results,…
• Product's name, description, manufacturer, price,…
• Book's publisher, author, title,…
• facts about relationships
• BADER lives in Riyadh
• Nora bought a book from university books shop on
01/03/11
• Notice the different types of data
• numbers, strings, text, date, time, timestamp,
• Text, picture, audio, video, graphics …
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• Data: Known facts that can be recorded and have an
implicit meaning. ex)What does 3421 means?
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Data versus Information
 Data itself has no meaning without meta data which describes
data
 For example :
 Does not give us any information, but knowing the meta data
that explains data : Staff_ID, Phone Number, room number
Staff_ID
Phone Number
1012674
28761
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 1012674, 28761, 153
room number
153
 Information : is the data you process in a manner
that makes it meaningful.
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Database
 Database
Data: name
city
birth
Khaled Dammam 01/01/70
Sara
Abha
01/03/01
Metadata: name - string, length<10
city – string, length<15
birth – date, format DD/MM/YY
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A collection of logically related data, including metadata
- ”data about data”, that describes data
Data is what you store in database
Information is what you retrieve from database
 Two examples
 all data required for the management of student records in a university.
 all data required for the management of books and borrowers in a
library.
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 Numeric and Textual Databases
 Multimedia Databases
 Geographic Information Systems (GIS)
 Data Warehouses
 Real-time and Active Databases
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Types of Databases
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Example of a Database
(with a Conceptual Data Model)
 Mini-world for the example: Part of a UNIVERSITY
environment.
 Some mini-world entities:
 STUDENTs
 COURSEs
 SECTIONs (of COURSEs)
 Grade Report
 Prerequiests
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 Mini-world: Some part of the real world about which
data is stored in a database.
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Example of a Database
(with a Conceptual Data Model)
 SECTIONs are of specific COURSEs
 STUDENTs take SECTIONs
 COURSEs have prerequisite COURSEs
 INSTRUCTORs teach SECTIONs
 COURSEs are offered by DEPARTMENTs
 STUDENTs major in DEPARTMENTs
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 Some mini-world relationships:
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 Database Management System (DBMS)
A software system that enables users to
create, maintain, and query the database
Most DBMSs now have facilities that make
data access fast, reliable, secure and easy
 Example DBMSs
Oracle
MS Access
MySQL
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Database Management Systems
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• Database Application : is a collection of data
and the programs that interacts with the
database by issuing an appropriate request
(typically an SQL statement) to the DBMS.
• built on top of DBMS
• to satisfy end users special requirements and
preference
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Application programs
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• Purchases from the supermarket
• PNU Student Registration
• PNU Library
• Saudi Airline Reservation
• Purchases using your credit card
• Booking a holiday at the travel agents
• Using the Internet
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Examples of Database Applications
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 Database System: The DBMS software together with
the data itself. Sometimes, the applications are also
included.
(DB + DBMS + Application program)
 To manage large amounts of data
 Efficiently
 Reliably
 Securely
 conveniently
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Database System
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Database Approach
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• Self-describing nature of a database system: A DBMS
catalog stores the description of the database. The
description is called meta-data). This allows the DBMS
software to work with different databases.
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Main Characteristics of the Database
Approach
• Insulation between programs and data: Called programdata independence. Allows changing data storage
structures and operations without having to change the
DBMS access programs (application program).
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• Data Abstraction: A data model is used to hide storage
details and present the users with a conceptual view of
the database.
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Main Characteristics of the Database
Approach
• 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.
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Views
• Allows each user to have his or her own view of
the database.
• A view is essentially some subset of the
database.
• Benefits:
• Reduce complexity
• Provide a level of security
• Present a consistent, unchanging picture of the
structure of the database, even if the underlying
database is changed
Pearson Education © 2009
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 Sharing of data and multiuser transaction processing :
allowing a set of concurrent users to retrieve and to
update the database. Concurrency control within the
DBMS guarantees that each transaction is correctly
executed or completely aborted.
 Transaction: executing program or process that
includes one or more database accesses, such as
reading or updating of DB record
 OLTP (Online Transaction Processing) is a major part of
database applications.
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Main Characteristics of the Database
Approach
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• Hardware
• Can range from a PC to a network of computers.
• Software
• DBMS, operating system, network software (if
necessary) and also the application programs.
• Data
• Procedures
• Instructions and rules that should be applied to the
design and use of the database and DBMS.
• People
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Components of DBMS Environment
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Components of DBMS Environment
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Database Users
Communicate
User
Requirement
Write
DB Designer
Application
programmer
Write
System Analyst
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Procedure
Design
Program
Manage
Use
Naïve End User
Use
Sophisticated End
User
App
Program
DBA
DBMS
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DB
H/W
Database Users
• System Analyst: Determine the user requirements
• Database Designers:
• responsible for defining the content, the structure,
the constraints, and functions or transactions
against the database.
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and develop the system specifications.
• Application Programmer
•
•
Implement programs meet the end user needs
Test , debug , document, and maintain transactions
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Database Users
•
•
•
•
authorizing access to the database
coordinating and monitoring the DB use
acquiring software, and hardware resources
monitoring efficiency of operations.
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• Database administrators: responsible for:
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Database Users
Naïve : (Queries / modifies data)
- they make up a large section of the end-user
population.
- They use previously well-defined functions in the
form of “canned transactions” against the
database.
- Examples: bank-tellers or reservation clerks.
Sophisticated : Forms requests in a database query
language.
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• End-users: they use the data for queries, reports and
some of them actually update the database content.
• Categories of End-users:
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Advantages of Using the Database
Approach
• Controlling redundancy in data storage and in
• Sharing of data among multiple users.
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development and maintenance efforts.
• Restricting unauthorized access to data.
• Providing persistent storage for program Objects
• Providing Storage Structures for efficient Query
Processing
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• Providing backup and recovery services.
• Providing multiple interfaces to different
classes of users.
• Enforcing integrity constraints on the
database.
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Advantages of Using the Database
Approach
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• Complexity
• Cost of DBMS
• Additional hardware costs
• Performance
• Higher impact of a failure
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Disadvantages of Database Approach
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References
• “Database Systems: A Practical Approach to
Design, Implementation and Management.”
Thomas
Connolly,
Carolyn
Begg.
5th Edition, Addison-Wesley, 2009.
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• Main Reference:
• Supplementary:
• Fundamentals of Database Systems", Ramez
Elmasri, Shamkant B. Navathe, Addison Wesley,
The Latest Edition.
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