THE WORLDS OF DATABASE SYSTEMS Chapter 1 THE WORLDS OF DATABASE SYSTEMS

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

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.

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.

The Evolution of Database Systems Section 1.1 The Evolution of Database Systems

1.1 The Evolution of Database Systems 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?

1.1 The Evolution of Database Systems (cont'd) A DBMS is expected to: Allow users to create new databases by declaring the logical structure of the data (schema) using a specialized language called Data Definition Language (DDL). 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). Support the storage of huge amount of data using very efficient access methods.

1.1 The Evolution of Database Systems (cont'd) A DBMS is expected to: (cont'd) Enable durability, the recovery of the data in the case of failures. Control access to data from many users concurrently without any unexpected interactions (called isolation)

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

1.1.1 Early Database Management Systems 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.

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 high- level query language.

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.

1.1.2 Relational Database Systems 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.

1.1.3 Smaller and Smaller Systems 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!

1.1.3 Smaller and Smaller Systems 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.

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: Google holds petabytes of data for its crawler of the Web. Satellites send down petabytes of information. Amazon keeps millions of products' picture and info. YouTube keeps millions of movies. And so forth ...!

1.1.5 Information Integration 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?

1.1.5 Information Integration 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.

Overview of a Database Management System Section 1.2 Overview of a Database Management System

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

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

Outline of Database-System Studies Section 1.3 Outline of Database-System Studies

1.3 Outline of Database-System Studies

References for Chapter 1 Section 1.4 References for Chapter 1

References for Chapter 1