Introduction to

Databases

“When I use a word,” Humpty Dumpty said in rather a scornful tone,

“it means just what I choose it to mean - neither more nor less.”Lewis Carroll, Through the Looking Glass

Class Outline

What is data and why is it important? What is a database and database schema? What is a database management system? What is a database application and what are its

components? What are the levels of database representation? What were the limitations of the systems that led to the

development of the current relational database systems? What are various types of database systems? What is a table, file and record?

When do I use a Database program?

Word processing

Spreadsheet

Text handling excellent fairMathematical functions poor excellent

Ease of Use excellent good

Training Cost low moderate

Software Cost low moderate

Volume of data low moderate

Multiuser Access low moderate

Database

poor

very good

fair

high

high

very high

very high

Word processing

Spreadsheet

Text handling excellent fairMathematical functions poor excellent

Ease of Use excellent good

Training Cost low moderate

Software Cost low moderate

Volume of data low moderate

Multiuser Access low moderate

Database

poor

very good

fair

high

high

very high

very high

Principles of Information Resource Management

Organizational resources flow into and out of the organization Two types of major organizational resources: Physical resources,

Conceptual resources (data & information) As scale of organization grows, it becomes increasingly difficult

to manage by observation (i.e., reliance on conceptual resources) Conceptual resources can be managed just like physical resources

or assets (e.g., employees, $$, equipment, widgets, etc.) Management of data & information means getting it before it’s

needed, protecting it, assuring quality, and getting rid of it when no longer required

Management of data & information can be achieved only through organizational commitment

Adapted from McFadden, F.R. & Hoffer, J.A. (1994). Modern Database Management. Redwood City, CA:Benjamin/Cummings Publishing (p. 6)

Information is a major organizational resourcepr

oces

sing

Jane bought 30 in JulyJane bought 20 in Aug

John bought 50 in JulyJohn bought 10 in AugData

(isolated facts)

Average/ July is 40

Average/ Aug is 15Information(organized data)

Sales have dropped between July and August

Knowledge

Survey customers; invest in advertising; cut costs, expand product line

Action

What is a Database?

Organized collection of related information or data stored on a computer disk for easy, efficient useOrderNum InvoiceAmt CustomerName Ow nerName Phone

201 854.00 Cottage Grill Ms. Doris Reaume (616) 643-8821

209 1,106.00 Cleo's Dow ntow n Restaurant Ms. Joan Hoffman (616) 888-2046

214 1,070.50 Jean's Country Restaurant Ms. Jean Brooks (517) 620-4431

221 1,607.00 Maxw ell's Restaurant Ms. Barbara Feldon (219) 333-0000

235 1,004.50 Embers Restaurant Mr. Clifford Merritt (219) 816-2456

239 1,426.50 The Empire Ms. Curtis Haiar (616) 762-9144

Outstanding Invoice Amounts By Order

201

209

214

221

235

239

data

information

(e.g., Oracle, dBase,

Access, Paradox)

Database DBMSDatabase

Application

user

What is a Database Management System (DBMS)?

“A set of programs used to define,administer, and process the database and its applications conveniently and efficiently”Program (or collection of programs) that enables users to create the database. The DBMS manages the storage and retrieval of data, and provides the user with certain functionalities to guarantee that the data will be logically organized and consistently applied.

What is a Database Application?

A computer program that performs a specific task of practical value in a business situationAn interface that allows the user to enter and manipulate data; User can request abstract views of dataCreated by database designers and developers using a DBMS program or a programming language

Database

DBMS

Database application

Major Components of a Database Application

3. Query- asks questions of data

1. Form- data entry 2. Report- summarizes & prints

5. Program - used to automate a database

4. Menu - organizes components

Features of a DBMS

DBMS

Engine

Database• user data• metadata• indexes• application

metadata

Design Tools Subsystem• Table Creation Tool• Form Creation Tool• Query Creation Tool• Report Creation Tool• Procedural Language

Compiler

Applicationprogram

developer

Run Time Subsystem• Form Processor• Query Processor• Report Writer• Procedural Language

RunTime Applicationprogram

users

DBMS

Types of Database Systems

Distributed >1 site, requires networknot widely adapted yet due to many problems

Centralized (single site)microcomputer (desktop)legacy mainframe/ mini computer (1

CPU)client/server architecture (>1 CPU)

our focus;centralized,micro-computerdatabase

Type Example# of concurrent

users

PersonalJoe's House Painting Service

1

Workgroup Video rental store < 25

Organizational (enterprise)

Larger Corporations or Government

hundreds

Multimedia (Internet technology)

Holiday resort bookings (with photos)

possibly hundreds

Typical size of database

Any

> 1 Trillion bytes

< 100 Megabytes

< 10 Megabytes

Three levels of Database Representation

database

design,

logical,

abstract

description of

data elements

& their

relationships

Conceptual level

physical implementation

- access methods, index construction,

data structure; database exists in reality only

here

Internal level

Primary focus of the lectures of this course is the conceptual level because the creation of a database begins with its design; the focus of the laboratories

is the external level, using a RDBMS, which manages the internal level.

External level

each user

group will

have its own

view of the

database;

database is

accessed from

here

Focus of this course

Lectures Conceptual design of

databases: determining their purpose, developing a model, identifying the tables that are required, designing normalized tables and identifying their relationship to one another.

Laboratories Implement a database at

the external level: create databases (tables) and database applications (queries, forms, reports, programs) using a typical microcomputer relational database management system, MS Access 97.

The Database System Environment

Hardware - physical devices computer, peripherals, network devices

Software DBMS (manages the database) operating systems software (manages hardware & software) application programs (user access and manipulate database)

People system administrators (manage general operations) database designers (architects of database structure) database administrators (ensure the database is functioning) systems analysts & programmers (design & implement database) end users (use application programs)

Procedures - rules of the company governing use of data Data

you are here

In the beginning…(in the 1950s)

…There were no databases. Just file (or data processing) systems.

Name: Jane Doe Address: 123 Easy St.City: LondonPhone: 455-0897

Date: Sept 14, 1955Time: 2:00 p.m.Patient: Jane Doe, 455-0897OHIP: 123456789

File systems were typically organized by function (use)

The first data management systems performed clerical tasks (transactional processing) such as order entry processing, payroll, work scheduling.

e.g., files for patients (file folder analogy); each record for a single patient; another file for appointment/ billing information

Limitations of Data File Systems

Worked adequately if data collection needs were relatively small. Problems arose as data files, information needs, and reporting

requirements grow in complexity due to: Extensive programming - use of third-generation languages (e.g.,

COBOL, FORTRAN) in which the programmer must specify what is be done as well as how it is to be done

Customerfile

CustomerprocessingApplication

Orderfile

OrderprocessingApplication

Limitations of Data File Systems

Poor mechanisms for sharing data across organization - files

are often incompatible with one another (separate, isolated data)

Data redundancy - duplicate information in two or more files

Program/ data dependence - if the file structure changed,

ALL programs using the file had to be modified - time-

consuming

Lack of flexibility - could not do ad hoc queries or reports;

required separate programs for every report or query

Poor security - difficult to program, therefore, often omitted

Difficulty of representing data in the users’ perspective

Historical Roots of Database Systems

Developed to overcome limitations of file systems, developed initially on mainframe computers in late 60s and early 70s - a typical early DBMS cost $100,000 (many are still in use)

First general databases were created for General Electric Company (GEC) - Integrated Data Store (IDS), designed to run on GEC machines; B.F. Goodrich ported IDS to IBM 360 - became dominant until 1980s

As PCs gained popularity (1980s), single-user, personal databases developed; at present, most database technology is used in workgroups

DatabaseDBMS

CustomerprocessingApplication

OrderprocessingApplication

EmployeeprocessingApplication

`

`

Better Definition of a Database

A collection of users’ data, organized logically and managed by a unifying set of principles, procedures, and functionalities, which help guarantee the consistent application and interpretation of that data

(a) organized collection of related information or data stored on a computer disk for easy, efficient use; represented in tabular format

OrderNum InvoiceAmt CustomerName Ow nerName Phone

201 854.00 Cottage Grill Ms. Doris Reaume (616) 643-8821

209 1,106.00 Cleo's Dow ntow n Restaurant Ms. Joan Hoffman (616) 888-2046

214 1,070.50 Jean's Country Restaurant Ms. Jean Brooks (517) 620-4431

221 1,607.00 Maxw ell's Restaurant Ms. Barbara Feldon (219) 333-0000

235 1,004.50 Embers Restaurant Mr. Clifford Merritt (219) 816-2456

239 1,426.50 The Empire Ms. Curtis Haiar (616) 762-9144

Better Definition of a Database (cont'd)

(b) A database is self-describing (metadata or system catalogues or data dictionary) A database contains a description of its own

structure (e.g., the names of all the tables, the names and types of data in each column in all the tables)

Kroenke, D.M., Database Processing: Fundamentals, Design & Implementation, Prentice Hall, 1998

Better Definition of a Database (cont'd)

(c) Indexes are stored with the database Data accessed from a source table for sorting and searching is

time-consuming without a “pointer” system, which improves performance and accessibility of the database

The “overhead cost” of indexing is that each time data is updated, all indexes must also be updated, therefore, reserve index for cases in which they are needed

Salesperson

Employee ID Name Office27 Rodney Jones Toronto44 Goro Azuma Tokyo35 Francine Moire Brussels37 Anne Abel Tokyo

Office Index

Office Employee IDToronto 27Tokyo 44, 37Brussels 35

(d) Application Metadata - stores structure and format of application components; not all DBMS support this feature

Evolution of Database Models

Hierarchical

Network

Relational

Semantic

Object-Oriented

Object-Relationa

l

still in use in many older (1970s) legacysystems; very few new databases;referred to “navigational systems”

the vast majority currently use this, therefore, our course’s focus is here

Very few new databases are being created using Object-Oriented Programming (not many ODBMS for businesses to implement this model)

The Relational Database Model

Agents

Clients Entertainers

Engagements Entertainer styles

Instruments

represented by tables (like spreadsheets) tables are NOT linked with physical pointers unlike earlier systems, all three types of relationships can be

represented accommodates the design of larger databases that involve

complex relationships and intricate manipulations

But #1 problem still is

Evaluation of the Relational database model

Advantages mechanisms for minimizing data redundancy and inconsistency logical database design is separated from physical aspects relatively program-data independent management of data for access, manipulation, and security flexible mechanisms for generating reports and queries program development and maintenance costs are reduced data can be accessed in a multiplicity of ways within and

amongst organizations

Disadvantages ease of use - many untrained people create and use databases

without considering its design - usually incorporate many errors

Comparison of Database models

Hierarchical, Network DBMS• data independence• structural dependence• demands upon programmer

Relational DBMS• data independence• structural independence• demands upon computer

File Systems• data dependence• structural dependence• demands upon

programmer

table = file = relation

Table

Users view their data in two-dimensional tables.

column = field = attribute

Field

The fields within records contain data.Data within a field must be of the same data type. Each field within a table must have a unique name. Order of fields is unimportant.

row = record = tuple

Record

A record is a group of related fields of information about a single instance of one object or event in a database.

Tables consist of zero, one, or more records. Order of rows is unimportant.

Database Schema

Database schema defines database’s structure, tables, relationships, domains, and constraint rules

Tables BOOK (ISBN, Title, AuthID, PubID, Price) PUBLISHER (PubID, PubName, PubPhone) AUTHOR (AuthID, AuthName, AuthPhone)

Relationships Each book is published by one and only one publisher Each publisher publishes one or more books

Domains (set of values in a column) Physical description (e.g., set of integers 0 < x < 99999)

Constraints (business rules) Price cannot be less than zero; Author phone field cannot be left

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