Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011 Chapter 1 THE WORLDS OF DATABASE SYSTEMS 1

Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011 The Worlds of Database Systems 1.1 The Evolution of Database Systems 1.2 Overview of a Database Management System 1.3 Outline of Database-System Studies 1.L4 Big Data- Reading material 1.4 References for Chapter 1 2

Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011 The Worlds of Database Systems 1) Databases are involved with almost every business in the world. 2) Almost any website has a database behind the scene that serving up the information you request. 3) Big Data on the Clouds 3

Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011 The Worlds of Database Systems 3) Corporations maintain all their important records in databases. 4) The power of databases comes from a powerful software that has developed over several decades and is called a Database Management System or DBMS. 5) Big Data on the Clouds See the reading material 4

Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011 THE EVOLUTION OF DATABASE SYSTEMS Section 1.1 5

Dr. T. Y. Lin | SJSU | CS 157A | Fall The Evolution of Database Systems What is a database? What is a database? Database is a collection of information that exists over a long period of time, even many years. Database is a collection of information that exists over a long period of time, even many years. (TYLIN: when it starts, it never ends until dies) The term database refers to a collection of data that is managed by a DBMS. The term database refers to a collection of data that is managed by a DBMS. What the DBMS's do? What the DBMS's do? 6

Dr. T. Y. Lin | SJSU | CS 157A | Fall The Evolution of Database Systems (cont'd) A DBMS is expected to: A DBMS is expected to: 1. Allow users to create new databases by declaring the logical structure of the data (schema) using a specialized language called Data Definition Language (DDL). 2. Give users the ability to query (a question about the data) the data, modify the data using a specialized language called Data Manipulation Language (DML). 3. Support the storage of huge amount of data using very efficient access methods. 7

Dr. T. Y. Lin | SJSU | CS 157A | Fall The Evolution of Database Systems (cont'd) A DBMS is expected to: (cont'd) A DBMS is expected to: (cont'd) 4. Enable durability, the recovery of the data in the case of failures. 5. Control access to data from many users concurrently without any unexpected interactions (called isolation) 8

Dr. T. Y. Lin | SJSU | CS 157A | Fall The Evolution of Database Systems Early Database Management Systems Relational Database Systems Smaller and Smaller Systems Bigger and Bigger Systems Information Integration 9

Dr. T. Y. Lin | SJSU | CS 157A | Fall Early Database Management Systems The first DBMS's appeared in the late 1960's. The first DBMS's appeared in the late 1960's. These systems evolved from file systems that could just store large amount of data over a long period of time. These systems evolved from file systems that could just store large amount of data over a long period of time. They did not support the requirements we counted in previous slides. They did not support the requirements we counted in previous slides. 10

Dr. T. Y. Lin | SJSU | CS 157A | Fall Early Database Management Systems (cont'd) The first important applications of DBMS's are: The first important applications of DBMS's are: Banking systems Banking systems Airline reservation systems Airline reservation systems Corporate record keeping Corporate record keeping The early DBMS's used several different data models like 'hierarchical' or tree-based model and 'network' or graph-based model. The early DBMS's used several different data models like 'hierarchical' or tree-based model and 'network' or graph-based model. These early DBMS's did not support a high- level query language. These early DBMS's did not support a high- level query language. 11

Dr. T. Y. Lin | SJSU | CS 157A | Fall Relational Database Systems Relational Model (RM) was born in 1970 by a famous paper written by Ted Codd. Relational Model (RM) was born in 1970 by a famous paper written by Ted Codd. TYLin: David Hsiao Column based RM Codd proposed a new two dimensional (table) organization of data, which in pure mathematics is called relation. Codd proposed a new two dimensional (table) organization of data, which in pure mathematics is called relation. 12

Dr. T. Y. Lin | SJSU | CS 157A | Fall Relational Database Systems In this new model, the programmers were not involved with the storage structure. In this new model, the programmers were not involved with the storage structure. Queries could be expressed in a very high-level language. Queries could be expressed in a very high-level language. By 1990, relational database systems were the norm. By 1990, relational database systems were the norm. 13

Dr. T. Y. Lin | SJSU | CS 157A | Fall Smaller and Smaller Systems Originally, DBMS's were large, expensive software running on large computers. Originally, DBMS's were large, expensive software running on large computers. The size was necessary because storing a gigabyte of data required a large computer. The size was necessary because storing a gigabyte of data required a large computer. But today, hundreds of gigabytes fit on a single disk and we can put it on a laptop! But today, hundreds of gigabytes fit on a single disk and we can put it on a laptop! 14

Dr. T. Y. Lin | SJSU | CS 157A | Fall Smaller and Smaller Systems Another important trend (may not be there any more) is the use of documents using XML (eXtensible Modeling Language). Another important trend (may not be there any more) is the use of documents using XML (eXtensible Modeling Language). (In CS267) Large collections of small documents can serve as a database, and methods of querying and manipulating them are different. (In CS267) Large collections of small documents can serve as a database, and methods of querying and manipulating them are different. 15

Dr. T. Y. Lin | SJSU | CS 157A | Fall Bigger and Bigger Systems A gigabyte is not much data anymore! A gigabyte is not much data anymore! Corporate routinely use terabytes(10 12 bytes) and petabytes (10 15 bytes) of data storage. Here are some examples: Corporate routinely use terabytes(10 12 bytes) and petabytes (10 15 bytes) of data storage. Here are some examples: Google holds petabytes of data for its crawler of the Web. Google holds petabytes of data for its crawler of the Web. Satellites send down petabytes of information. Satellites send down petabytes of information. Amazon keeps millions of products' picture and info. Amazon keeps millions of products' picture and info. YouTube keeps millions of movies. YouTube keeps millions of movies. And so forth...! And so forth...! 16

Dr. T. Y. Lin | SJSU | CS 157A | Fall Information Integration Consider a large company with many divisions. Consider a large company with many divisions. Each division has its own database for its products and employees independent of other divisions. Each division has its own database for its products and employees independent of other divisions. How can we integrate the information? How can we integrate the information? 17

Dr. T. Y. Lin | SJSU | CS 157A | Fall Information Integration One popular approach is the creation of data warehousing where information from many legacy databases is copied periodically. One popular approach is the creation of data warehousing where information from many legacy databases is copied periodically. Another approach is the implementation of a middleware to integrate and translate data. Another approach is the implementation of a middleware to integrate and translate data. 18

Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011 OVERVIEW OF A DATABASE MANAGEMENT SYSTEM Section

Dr. T. Y. Lin | SJSU | CS 157A | Fall Overview of a Database Management System Data-Definition Language Commands Overview of Query Processing Storage and Buffer Management Transaction Processing The Query Processor 20

Dr. T. Y. Lin | SJSU | CS 157A | Fall Data-Definition Language Commands 21

Dr. T. Y. Lin | SJSU | CS 157A | Fall Overview of Query Processing 22

Dr. T. Y. Lin | SJSU | CS 157A | Fall Storage and Buffer Management 23

Dr. T. Y. Lin | SJSU | CS 157A | Fall Transaction Processing 24

Dr. T. Y. Lin | SJSU | CS 157A | Fall The Query Processor 25

Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011 OUTLINE OF DATABASE-SYSTEM STUDIES Section

Dr. T. Y. Lin | SJSU | CS 157A | Fall Outline of Database-System Studies 27

Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011 REFERENCES FOR CHAPTER 1 Section

Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011 References for Chapter 1 29