Database Systems COMSATS INSTITUTE OF INFORMATION TECHNOLOGY, VEHARI

Instructor: Komal Chaudhary ◦MS(CS) – Silver Medalist

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 in- between 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 Hierarchical Database Relational 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