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Introduction to Database Management Systems Atul Kahate ALWAYS LEARNING PEARSON PDF

12 Pages·2017·0.96 MB·English
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Introduction to Database Management Systems Atul Kahate ALWAYS LEARNING PEARSON Introduction to Database Management Systems Introduction to Database Management Systems \ GO / o—- ——o mr \ sa J 'w a Atul Kahate PROJECT MANAGER /-I/ex Solutions Limited Pane Pearson Education This page is intentionally left blank. Copyright © 2004 by Pearson Education (Singapore) Pte. Ltd. Licensees of Pearson Education in South Asia No part of this eBook may be used or reproduced in any manner whatsoever without the publisher's prior written consent. This eBook may or may not include all assets that were part of the print version. The publisher reserves the right to remove any material in this eBook at any time. ISBN 9788131700785 elSBN 9788131775820 Head Office; A-8(A), Sector 62, Knowledge Boulevard, 7th Floor, NOIDA 201 309, India Registered Office; 11 Local Shopping Centre, Panchsheel Park, New Delhi 110 017, India This page is intentionally left blank. To My Wife Anita For being the best life partner one could ever hope to find Daughter Jui For being so wonderful, lovely, mischievous and cheerful Son Harsh For adding some spice to our small but brilliant family Jorezuord Like many technologies in the computer industry, the evolution of databases can be tracked back to research into automating office functions in the 1960s and 1970s. Firms discovered it was becoming far too expensive to hire people to do certain jobs such as storing and indexing files. They began investing in research into cheaper and more efficient mechanical solutions. In 1970, an IBM researcher named Ted Codd published the first article on relational databases. It outlined an approach that used relational calculus and algebra to allow non-technical users to store and retrieve large amounts of information. Codd envisaged a system where the user would be able to access information stored in tables with "natural language" commands. The article's significance was not recognised because it was far too technical and relied heavily on mathematics. However, it did lead to IBM starting a research group known as "System R". Eventually, System R evolved into SQL/DS which later became DB2. The language created by the System R group, SQL (Structured Query Language) has become the industry standard for relational databases and is now an ISO standard. The first database systems built upon the SQL standard appeared at the beginning of the 1980s from Oracle with Oracle Version 2, and later SQL/DS from IBM, as well as a host of other systems from other companies. Relational database technology was continually refined during the 1980s. This was due to feedback from customers, the development of systems for new industries and the increased use of personal computers and distributed systems. By the middle of the 1980s, it had become obvious that there were several fields where relational databases were not practical due to the types of data they used. These areas included medicine, multimedia and high energy physics and they needed more flexibility in how their data was represented and accessed. This led to research into object oriented databases where users could define their own methods of access to data and how it was represented and manipulated. This coincided with the introduction of Object Oriented Programming languages such as C-H- which started to appear in industry at the same time. Since then, in the late 1990s and the early years of this decade, we have seen huge advances in the technology behind running databases and securing them. Since their arrival, databases have expanded in size from the 8MB of data that System R had been tested with to terabytes of data used for mailing lists, credit card information for banks and so on. With each increase in the amount of storage available, we have seen a corresponding increase in the size and complexity of database systems in operation. In today's scenario, databases are ubiquitous in all modern corporations, so much so, that professionals carry smaller databases on palmtops or mobile phones. It will be hard to find any successful organisation that does not deploy databases for their key operations. This subject is now viii Foreword being taught and discussed in primary schools in urban areas. This area of technology has spun off a huge cottage industry around it, spanning from the technical support novice to highly specialised very large database management gurus. It is in light of this background that Atul's book is very significant. Effective database management has become a critical success factor in corporate IT strategy. Although, there are a number of books on this subject available in the market today, Introduction to Database Management Systems stands out because of the wide range of topics that it covers and the simple and lucid manner in which it explains them. It will be of tremendous value to students of this subject, who can also use it as a reference tool. While working with Atul over the years, I have always been impressed with his thorough under- standing of database management and other related topics. He also has outstanding ability to present his thoughts in the most palatable fashion. I am delighted that he has come out with this book that explains the theory behind database systems, their architectures and issues in a way that even a layman can understand. Atul has put to good use his practical experience while working with us at i-flex, mixed with his very good grasp of theory of databases. I wish him all the best in his future endeavours. Deepak Ghaisas CEO (India Operations) i-flex Solutions Limited Pune (Preface The traditional mechanism for storing computer data was data files. Data files have been immensely popular since the 1960s. The earlier commercially successful programming languages such as COBOL had extensive features related to file processing. In fact, even today, many major computer applications run on file-based computer systems. However, all this has also changed in the last few decades. Database Management Systems (DBMS) has become a subject of great significance in the Information Technology industry. Most serious business applications need the presence of DBMS in some form or the other. DBMS is replacing files as the de facto standard for storing data that is medium/long term in nature. This is especially true in the case of most newly developed applications. DBMS is a fascinating subject. Many people confuse it with Structured Query Language (SQL). However, SQL is just one aspect of DBMS technology. Understanding how DBMS technology really works involves the study of many theoretical concepts, such as database design, modelling, transaction management, security, concurrency, and so on. I have read a number of books on DBMS. Most of them explain DBMS technology quite well, but there is one aspect that I find quite intimidating, and that is the complexity of these books. I have a strong and sincere belief that without using almost any jargon and mathematics, we can study most aspects of the DBMS technology. It is intimidating to see complex mathematics and cryptic symbols one page after the other when learning DBMS. That is the sole reason why I have attempted to keep the material as simple as it can get. The idea is that even a person with very little background in computers will be able to grasp the main concepts in DBMS, and if he/she is interested, can go ahead and study the more complex features. Here are the main features of the book. ■ Orientation: An attempt has been made to cover the topics in an appropriate sequence, so that it is sufficient for the managers/professionals/teachers/students to refer to this book alone for learning about DBMS. ■ Contents'. The book covers all the major concepts in the DBMS technology that a reader at any level needs to understand. ■ Style: An attempt has been made to keep the language very simple and to make the explanations extremely lucid. ■ Visual approach: The book features a number of illustrations and diagrams (close to 400) to enable an easier grasp of the subject. ■ Pedagogical features: Every chapter contains a list of Key Terms and Concepts, Chapter Summary and self-study questions in the form of True/False questions, Multiple-choice questions and Detailed questions. In addition, Exercises are also provided at the end of every chapter. The chapter-wise organisation of the book is as follows. Chapter 1 provides a lot of background material to the subject of DBMS. This chapter covers the

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access information stored in tables with "natural language" commands. The article's It is in light of this background that Atul's book is very significant.
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