Introduction 1

Principles of Database SystemsWith Internet and Java Applications

Today’s Topic

Course Introduction

Instructors name and contact info goes here.

Please see the notes pages for additional comments.

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Outline of Course Study of principals and techniques of

databases Grades assigned as in information sheet Examples of use of databases Programming projects in database design and

implementation– Programming in Microsoft Access– Programming in Java with Oracle– Development of a web site with database support

Course notes in http://YOURWEBSITE Homework 1 due

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Textbook and class meetings Principles of Database Systems With Internet

and Java Applications– by Greg Riccardi– copyright 2001, Addison-Wesley

Lectures and recitations

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Students’ Role in Class Attend class, please.

– The class notes are available, but they are not the full classroom experience

– Recitation sections are provided to personalize and enhance your learning environment

– You are paying for this, take advantage of it Read the book.

– There are many topics covered in the text, but not the lectures

– There are many details and examples in the text Get copies of lecture notes

– Available the night before class Seek help during office hours

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Current Events Each lecture will cover current events that

affect the database industry Please bring info to lectures and recitations Today

– Las Vegas Consumer Electronics Show• www.zdnet.com/zdnn/special/ces2000.html

– Tallahassee Democrat Online• www.tdo.com

– New York Times technology• www.nytimes.com/yr/mo/day/tech/

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Why Study Files and Databases? Next few slides address the following

– Importance of Databases to Economy• Can you get a job in the database field?

– Representation of Information• Add meaning to data

– Management of Complexity• Divide system into layers, focus on data

– Management of Access and Security– Efficiency of Access and Storage

• Separate data, allow optimizations

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Importance of Databases to Economy Expanding use of databases in retail sales

– Walmart, retail sales information tracking– LL Bean, catalog sales information tracking

Examples of analyses– Sales of items

• Comparisons between daily totals of items sold and items in inventory

• Seasonal variations in sales of specific and similar items• Relative sales of similar items with different features

– Market-basket collections (all items in a single purchase)• Average and variation in total purchase amount• Average and variation in number and price of items• Correlation between sales of items in a single purchase

– Customer analysis• Behavior of average customer• Preferences of individual customers

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Importance of Database Companies Oracle is the 2nd largest software company

– It’s stock has outperformed S&P 500 and Microsoft

– This picture is the stock performance, as shown on the BigCharts Web site from July, 1999 to July, 2000

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E commerce Companies are fighting for the market

– See Oracle Web site– See IBM Web site

XML and XSL at Microsoft– http://www.microsoft.com/xml– http://msdn.microsoft.com/xml/demos/– http://msdn.microsoft.com/isapi/msdnlib.idc?

theURL=/library/techart/fm2koffice.htm

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Representation of Information

Data is collections of bits– physical database

Information is data with meaning– logical database

Representation of meta-data– database system is self-describing

Database Management System (DBMS)– define information content– construct database– manipulate by queries, reports and updates– data plus software

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Management of Complexity Insulation between programs and data

– Program-data independence– Program-operation independence– Data abstraction

• conceptual model for users• physical model for administrators

– Sharing data and multi-user transactions People

– Database administrators– Database designers– Applications programmers– End users

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Management of Access and Security Controlling redundancy

– inconsistency and duplication Restricting unauthorized access Enforcing integrity constraints Providing backup and recovery Persistent storage for program objects

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Efficiency of Access and StorageCost of Access for Seagate Cheetah Disk

Seek time– Move access arm to the cylinder– Avg 6 msec, min 0.6 msec

Rotational delay– 1000 rpm, one revolution per 6 millisecond– Average 3 msec

Total latency max 12 msec, avg 9 msec Transfer rate

– 24 Mbytes/sec

Speed of memory access, Athlon 750 mhz– Latency <100 nanosecond, 10,000 times faster than disk– Transfer rate 1.6 GBytes/sec, 7 times faster than disk

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Hierarchical Cost of Storage Registers and Cache are fixed size Primary storage, memory (RAM) limited by

hardware– 1000 Mbytes per CPU

Secondary storage, disk, also limited by hardware– 100 Gbytes per CPU

Tertiary storage, tape, etc. limited by storage volume

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Vocabulary Glossary of terms Define the terms as used in this subject

– Database literature is filled with terms Example of terms

– Data, bits– Information, bits with meaning (type)– Entity– Schema

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Client-server computing Examples from web sites

– New York Times– Pricewatch

Industry movement

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What is a Database? Database is a collection of data

– data is known facts with implicit meaning– database is logically coherent, organized.– database is designed, built and populated for a

specific purpose. Database management system

– collection of programs which support creation and maintenance of databases.

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Time Line for Database Systems before 1960 transition from punched card and tape 1960s, from file management to databases

– Bachman (GE) IDS and data structure diagrams– IMS from IBM, Hierarchical Data Model– IMS DB/DC, Network Model and communication– SABRE, multi-user access with network

1970s, CODASYL and Relational Model– Codd (IBM) Relational Model– Chen introduced Entity Relationship Model– Query languages developed (SQL)

1980s, Client/Server DBs, Oracle, DB2– PC databases, DBase, Paradox, etc.– SQL standard for definition and manipulation

1990s, web-based information delivery– Trends: expert DBs, object DBs, distributed DBs

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Concepts and Architecture

Data Model is a set of concepts that can be used to describe the structure of a database– data types, relationships, and constraints– basic operations, for retrieval and updates– user-defined operations, behavior

3 types of data models– High level or conceptual model

• entities,attributes, and relationships– low-level or physical model

• record formats, indexes and access paths– representational or implementation model

• record structures or object models

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Data Modeling A data model is a specification of the

information content of a system– conceptual data model describes information in

terms the users will understand– logical data model describes information in a way

that can be used to build a database– physical data model describes information in terms

of its representation in physical storage

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Schemas and Instances Schema is the structure of a database

– intention or meaning of the data– data models are schemas– table definitions are schemas– class definitions are schemas

Instances are the contents of a database– extension or values of the data– objects are instances– objects in a database are typically rows in a table

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Levels of database schemas Different schemas are presented to different

users

External level

internal to logical mapping

logical to external mappings

disk

Internal Schema Internal level

External View 1 External View 2 External View 3

Logical Schema Logical level

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Data Independence Logical data independence

– Change in conceptual schema does not require change in external schemas

– Expand or contract database with no change to external applications

– View mappings must be changed Physical data independence

– Change in internal schema does require change in conceptual schema

– Reorganize the file and index structure, especially for improved performance

– Conceptual mapping must be changed

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Database Languages

DDL, data definition language, conceptual schema– describe conceptual schemas

SDL, storage definition language, internal schema– describe file structures, indexes

VDL, view definition language, external schema DML, data manipulation language

– High-level or non-procedural (e.g. SQL)• Select Last Name from Roster where Section = 2

– Low-level or procedural• For r in Roster loop

if r.section = 2 thenresult.Add ( r.lastname );

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Examples of Use of Microsoft Access In class,

– Sample from Homework 1– Sample of class roster– Queries– Reports– Use of Access to create interfaces