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Transcript
Database Systems
COMSATS INSTITUTE OF INFORMATION TECHNOLOGY, VEHARI
Instructor:
Komal Chaudhary
◦ MS(CS) – Silver Medalist
komalchaudhary@ciitvehari.edu.pk
Division of Numbers
2 Sessional Exams = 25%
4 quizzes
4 assignments
Final exam = 50%
= 25%
Rules and regulations for the class
No eatables
No whispering
No late arrivals
Recommended Books
 Fundamentals of Database Systems
By Elmasri & Navathe
 Database System Concepts
by Abraham Silbershatz, Henery F. Korth, Sudarshan
Overview
• Data: Known facts that can be recorded
• Database: Collection of Integrated data – Typically models a real-world “enterprise”
• DBMS (Database management system): A software system designed to store, manage, and
facilitate access to databases.
Data vs. Information
• Data: Raw facts/Un-processed information
– But they are building blocks for information
• Information: Data Processed to reveal its meaning
– Information is meaningful
– In today’s world, accurate, relevant and timely information is the key to good decision making
– Good decision making is key to survival in today’s competitive and global environment
Files and Databases
• Files: A collection of records or documents dealing with one organization, person, area, or
subject. It could either be:
– Computer files
– Manual files (Paper)
• Database: A collection of similar records with relationships between records.
– Statistical, Business Data
Database
• A database is collection of stored operational data used by application systems of some
particular enterprise (C.J. Date)
• Will cover in detail
File processing systems
• Collection of application programs that performs services for the end-users (e.g. Reports)
• Each program defines and maintains 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.
• Atomicity of updates
– Failure may lead database to an inconsistent state with partial updates carried out – E.g.
Transfer of funds from one account to another should either be complete or incomplete, no inbetween state
Limitations of File-based approach
• Data dependence
– File structure is defined in the program code.
• Incompatible file formats
– Programs are written in different languages, and so cannot easily access each others files.
• Integrity Problems
– Hard to add new constraint or update existing one – File in the folder cannot keep such
conditions
Database Approach
• Overcomes problems associated with file
◦ - system based approach
• Central source of shared data
• The database holds not only the data but also a description of the data.
◦ – Data dictionary, or metadata
• A central location where data descriptions are stored.
• Data about data
◦ – Program-data independence
Advantages of Database Approach
• Program-data independence
◦ – The separation of data descriptions from the application programs that use the data.
◦ – Allows the data to change without changing the application programs.
• No or Planned data redundancy
• Improved data consistency
• Improved data sharing
• Enforcement of standards
Data processing models
Most computer processing systems require
some input from the user.
The way this processing is to be carried out is
determined at the system design stage of the
System Life Cycle.
Data processing models
Interactive processing, historically introduced as Time-sharing
◦ Accepts input from user
Transaction processing
◦ divided into individual, indivisible operations, called transactions.
◦ Each transaction must succeed or fail as a complete unit; it cannot be only partially complete.
Data processing models
Batch processing
◦ execution of a series of programs (jobs) on a computer without manual intervention
Real time processing
o study of hardware and software systems that are subject to a "real-time constraint"
Types of Databases
• Flat Files
• Hierarchical
• Relational
Relational Database
Hierarchical Database
Types of Databases
• Object Relational
• Object Oriented
• Web Enabled (Online DBs)
Database management system (DBMS)
Database management systems (DBMSs) are specially designed software applications that
interact with the user, other applications, and the database itself to capture and analyze data
 A general-purpose DBMS is a software system designed to allow the definition, creation,
querying, update, and administration of databases.
• Computerized library system
• Automated teller machines
• Flight reservation systems
DBMS Benefits
• Minimal data redundancy
• Consistency of data
• Integration of data
• Sharing of data
• Ease of application development
• Uniform security, privacy and integrity controls
• Data accessibility and responsiveness
• Reduced program maintenance
• Data independence
Components of DBMS
The major components of database management system are:
1.
Software
2.
Hardware
3.
Data
4.
Procedures
5.
Users
Components of DBMS
Hardware:
physical electronic devices
◦ such as computers (together with associated I/O devices like disk drives), storage devices
Software:
main component of a DBMS is the software
o Operating system, application programs, etc
Components of DBMS
Data:
main purpose of DBMS is to process the data
◦ update, delete, etc
Procedures:
instructions and rules that help to design the database and to use the DBMS
o User require procedures to run and operate DBMS
Components of DBMS
User:
The users are the people who manage the databases and perform different operations on the
databases in the database system
◦ Application Programmers
◦ Database Administrators
◦ End-Users