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Chapter 1
THE WORLDS OF
DATABASE SYSTEMS
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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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
1.4 References for Chapter 1
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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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.
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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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.
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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Section 1.1
THE EVOLUTION OF DATABASE
SYSTEMS
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1 The Evolution of Database
Systems
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
What is a database?
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.
What the DBMS's do?
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1 The Evolution of Database
Systems (cont'd)

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.
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1 The Evolution of Database
Systems (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)
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1 The Evolution of Database
Systems
1.1.1 Early Database Management Systems
1.1.2 Relational Database Systems
1.1.3 Smaller and Smaller Systems
1.1.4 Bigger and Bigger Systems
1.1.5 Information Integration
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1.1 Early Database Management
Systems

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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.
They did not support the requirements we
counted in previous slides.
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1.1 Early Database Management
Systems (cont'd)



The first important applications of DBMS's are:

Banking systems

Airline reservation systems

Corporate record keeping
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 highlevel query language.
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1.2 Relational Database Systems

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.
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1.2 Relational Database Systems


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In this new model, the programmers were not
involved with the storage structure.
Queries could be expressed in a very high-level
language.
By 1990, relational database systems were the
norm.
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1.3 Smaller and Smaller Systems

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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.
But today, hundreds of gigabytes fit on a single
disk and we can put it on a laptop!
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1.3 Smaller and Smaller Systems

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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.
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1.4 Bigger and Bigger Systems


A gigabyte is not much data anymore!
Corporate routinely use terabytes(1012 bytes)
and petabytes (1015 bytes) of data storage.
Here are some examples:
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Google holds petabytes of data for its crawler of the
Web.
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Satellites send down petabytes of information.
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Amazon keeps millions of products' picture and info.
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YouTube keeps millions of movies.
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And so forth ...!
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1.5 Information Integration
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Consider a large company with many
divisions.
Each division has its own database for its
products and employees independent of
other divisions.
How can we integrate the information?
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.1.5 Information Integration
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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.
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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Section 1.2
OVERVIEW OF A DATABASE
MANAGEMENT SYSTEM
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.2 Overview of a Database
Management System
1.2.1 Data-Definition Language Commands
1.2.2 Overview of Query Processing
1.2.3 Storage and Buffer Management
1.2.4 Transaction Processing
1.2.5 The Query Processor
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.2.1 Data-Definition Language
Commands
Dr. T. Y. Lin | SJSU | CS 157A | Fall 2011
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1.2.2 Overview of Query
Processing
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1.2.3 Storage and Buffer
Management
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1.2.4 Transaction Processing
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1.2.5 The Query Processor
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Section 1.3
OUTLINE OF DATABASE-SYSTEM
STUDIES
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1.3 Outline of Database-System
Studies
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Section 1.4
REFERENCES FOR CHAPTER 1
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References for Chapter 1
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