DBS Lecture#1

8/9/2019 DBS Lecture#1

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Database Systems:Introduction

Professor Navneet GoyalDepartment of Computer Science & Information Systems

BITS, Pilani


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Prof. Navneet Goyal, BITS, Pilani

Text BookHector G Molina, Jeffrey D.Ullman & Jennifer Widom.

Database Systems The Complete Book,Pearson Education, 2002.

Home Page:

http://www-db.stanford.edu/~ullman/dscb.html


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Reference Books Ramakrishna R. & Gehrke J.

Database Management Systems, 3e, Mc-Graw Hill,2003.http://www/cs.wisc.edu/~dbbook

Silberschatz A, Korth H F, & Sudarshan S.Database System Concepts, 5e, TMH, 2005.http://www.db-book.comhttp://www.mhhe.com/silberschatz

Elmarsi R, & Navathe S B.Fundamental of Database System, 4e, PearsonEducation, 2004.http://www.aw.com/cssupport


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Topics Evolution of Databases Data, Database, DBMS, & DBS Data Modeling Relational Databases Schema Design & Normalization Query Languages Storage & Indexing Query Processing & Optimization Concurrency Crash Recovery Advanced Topics


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Basic Definitions Database: A collection of related data. Data: Known facts that can be recorded and

have an implicit meaning.

Mini-world: Some part of the real world aboutwhich data is stored in a database. For example,student grades and transcripts at a university.

Database Management System (DBMS): Asoftware package/ system to facilitate thecreation and maintenance of a computerizeddatabase.

Database System: The DBMS softwaretogether with the data itself. Sometimes, theapplications are also included.


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DBMS Functionalities Define a database : in terms of data types,

structures and constraints

Construct or Load the Database on asecondary storage medium

Manipulating the database : querying,generating reports, insertions, deletionsand modifications to its content

Concurrent Processing and Sharing by a setof users and programs yet, keeping alldata valid and consistent

Crash Recovery


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File System vs. DBMS A company has 500 GB of data on

employees, departments, products, sales,& so on..

Data is accessed concurrently by severalemployees

Questions about the data must beanswered quickly

Changes made to the data by differentusers must be applied consistently Access to certain parts of the data be

restricted


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File System vs. DBMS Data stored in operating system files

Many drawbacks!!! 500 GB of main memory not available to hold all data.

Data must be stored on secondary storage devices Even if 500GB of main memory is available, with 32-bit

addressing, we cannot refer directly to more than 4GBof data

Data redundancy and inconsistency Multiple file formats, duplication of information in different

files

Special program to answer each question a user mayask


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File System vs. DBMS Many drawbacks!!!

Integrity problems Integrity constraints (e.g. account balance > 0) becomeburied in program code rather than being statedexplicitly

Hard to add new constraints or change existing ones

We must protect the data from inconsistent changesmade by different users. If application programs needto address concurrency, their complexity increasesmanifolds

Consistent state of data must be restored if the systemcrashes while changes are being made OS provide only a password mechanism for security.

Not flexible enough if users have permission to accesssubsets of data


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File System vs. DBMS These drawbacks have prompted the

development of database systems

Database systems offer solutions toall the above problems?


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Advantages of a DBMS Program-Data Independence

Insulation between programs and data: Allowschanging data storage structures and operations

without having to change the DBMS access programs. Efficient Data Access

DBMS uses a variety of techniques to store & retrievedata efficiently

Data Integrity & Security

Before inserting salary of an employee, the DBMS cancheck that the dept. budget is not exceeded

Enforces access controls that govern what data isvisible to different classes of users


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Advantages of a DBMS Data Administration

When several users share data , centralizing theadministration offers significant improvement

Concurrent Access & Crash Recovery DBMS schedules concurrent access to the data in such

a manner that users think of the data as beingaccessed by only one user at a time

DBMS protects users from the ill-effects of systemfailures

Reduced Application Development Time Many important tasks are handled by the DBMS


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Databases Everywhere!!! DBMS contains information about a particular enterprise

Collection of interrelated data Set of programs to access the data An environment that is both convenientand efficientto use

Database Applications: Banking: all transactions Airlines: reservations, schedules Universities: registration, grades Sales: customers, products, purchases Online retailers: order tracking, customized recommendations

Manufacturing: production, inventory, orders, supply chain Human resources: employee records, salaries, tax

deductions

Databases touch all aspects of our lives


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Levels of Abstraction Databases provide users with an

abstract view of data


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Levels of Abstraction

Many views, singleconceptual (logical)schema andphysicalschema.

Views describe how userssee the data.

Conceptual schema defineslogical structure

Physical schema describesthe files and indexes used.

Schemas are defined using DDL; data is modified/queried using DML.

Physical Schema

Conceptual Schema

View 1 View 2 View 3


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Q & A


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Thank You

Documents

DBS Lecture#1