Database

Database Management

An Introduction

Goals For Today:

Describe why databases have become so important to modern organizations

Describe what database and database management systems are and how they work.

Explain four emerging database trends:– (1) client / server computing, – (2) object-oriented databases, – (3) data mining, and – (4) integrating Web applications

Database Defined

Database: – A collection of related data organized in a way

that facilitates data searches. What are some examples of Databases?

Example of a Student Database

Types of Data Collected in a Typical Student Database

Databases Before the Use of Computers

Data was stored in:– books– ledgers– card files– folders– file cabinets– or simply in people’s heads!?

Computers make the process of storing and managing data easier

The Database Approach

Database Management System– software application which allows you to

create, store, organize, and retrieve data from a single database or many databases.

– Example: MS Access Entity

– something you collect data about– Examples: people or classes

A Database Contains the Following: Tables

– how entities are represented in a database, where each row is a record and each column a field.

Fields– individual pieces of information

Record– collection of related fields within one entity

Sample Data Table (page 2-94 in your book)

Key Database Issues and Activities Entering and Querying Data Creating Database Reports Data Structure Data Type

Entering Data

Data Entry:– process of getting information into a database– possible methods of data entry:

Data Entry Professional, Electronic Files, Historical Records, or Web Based (Forms)

Querying Data Querying:

– how we get information from a database Structured Query Language (SQL):

– most common language used to interface with databases

– Example:SELECT DISTINCTROW STUDENT_ID, GRADE

FROM GRADES

WHERE GRADE = “A”

ORDER BY STUDENT_ID;

Querying Data continued Query By Example (QBE)

– enables you to fill out a grid, or template, in order to construct a description of the data you would like to retrieve.

Creating Database Reports Report:

– A compilation of data from the database that is organized and produced in a printed format.

– Typically produced on paper, but also can be displayed on-screen.

– Example: Quarterly Sales Report

Data Structure

Database has two parts:– Data– Data Structure: how the data is organized.

Data Model:– representation of entities and their relationships to the

real world Primary Key:

– a unique identifier in the database– one or more fields

Data Structure continued

Primary Key is Student ID

Data Type

Data Type:– each field in the database needs to be of a

certain type– Examples: text, number, dates

Data Dictionary:– a document (often published online) prepared

by the database designers to aid users in data entry.

Data Dictionary Example:

Students Table

Primary Key Field Name Field Type Field Length

yes Student ID Number 9

no Last Name Text 20

no First Name Text 15

Database Management Systems Approaches The Hierarchical Model The Network Model Relational Model Normalization Associations

The Hierarchical Model Records in parent entities can have many

child records, but each child can have only one parent.

Parent

Child

The Network Model

In this case you can have multiple children and parents Parents

Children

The Relational Model– A good relational database design eliminates

unnecessary data duplications and is, therefore, easier to maintain

– Relationship: joining two tables on a common field

Relationship

Normalization

A technique used to make complex databases more efficient and easier to handle

Eliminates Redundant Data

Normalization continuedDatabase w/redundant data

Database after Normalization

Three Types of Associations or Relationships

– One-to-One Each team has only one home stadium, and each home stadium has

only one team– Team ID Team Name Location Stadium ID

– One-to-Many Each Player is on only one team, but each team has many players

– Player ID Player Name Position Team ID

– Many-to-Many Each player participates in many games, and each game has many

players

Team 1 Team 2 Date Player ID Points Minutes Fouls

Recent Developments AffectingDatabase Design and Use Databases and Client / Server Computing Object-Oriented Databases Data Mining Linking Web Site Applications to

Organizational Databases

Databases and Client / Server Computing

Database application is divided into two parts: – Database Server

where all data is stored on a powerful machine

– PC Client the program used to manipulate the data resides on an

individual user’s computer

Object-Oriented Databases

treat tables, queries, and other components as generic reusable OBJECTS (rather than data) that can be mixed and matched and used in many applications (e.g. MS Excel and MS Access).

Most of today’s database applications have some of these Object characteristics.

Data Mining

Allows companies to sort and analyze information to better understand customers, products, markets, or any other phase of their business for which data has been captured.

Example: Grocery Store Club Cards

Data Mining continued Data Warehouses

– An integration of multiple, large databases and other information sources into a single repository or access point that is suitable for direct querying, analysis, or processing

Data Warehouse Examples

TELECOMMUNICATIONS REPRESENTATIVE COMPANIES

Analysis of the following: AT&T

Call volumes Ameritech

Equipment sales Belgacom

Customer profitability British Telecom

Costs Telestra AustraliaTelecom Ireland

Inventory Telecom Italia

Purchasing leverage with suppliers

Frequent buyer program management

Data Mining continued Data Marts

– A small-scale data warehouse that contains a subset of the data for a single aspect of a company’s business

– Examples: finance, inventory, or personnel

Linking Web Site Applications to Organizational Databases Example:

– many comapies are enabling users of their Web Site to:

view product catalogs, check inventory, and place orders

these are all actions that read and write to the organizations’ databases.

Goals For Today:

Described why databases have become so important to modern organizations

Described what database and database management systems are and how they work.

Explained four emerging database trends:– (1) client / server computing, – (2) object-oriented databases, – (3) data mining, and – (4) integrating Web applications