Guide to Oracle 10g Chapter 1: Client/Server Databases and the Oracle 10g Relational Database

Guide to Oracle 10g

Chapter 1:

Client/Server Databases and the Oracle 10g Relational Database

Guide to Oracle 10g 2

Objectives

• Develop an understanding of the purpose of database systems

• Describe the purpose and contents of an entity-relationship model

• Explain the steps in the normalization process• Describe the differences between personal and

client/server databases

Guide to Oracle 10g 3

Objectives (continued)

• Understand the Northwoods University student registration database and the Clearwater Traders sales order database

Guide to Oracle 10g 4

Introduction

• If an organization needs to store and maintain a large amount of data that must be viewed and updated by many users at the same time, it often uses a client/server database such as Oracle 10g.

Guide to Oracle 10g 5

Database Systems

• Data files consist of:– Fields

• Describe characteristics

• Also called columns

– Records• Group of related fields

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Database Systems (continued)

• Problems with storing data in files:– Proliferation of data management programs

– Presence of redundant data

– Inconsistent data

• Database– Stores all organizational data in central location

– Eliminates redundant data to reduce possibility of inconsistent data

Guide to Oracle 10g 7

Database Systems (continued)

• Database management system (DBMS)– Application that performs all routine data-handling

operations

– Provides central set of common functions for managing database

• Inserting

• Updating

• Retrieving

• Deleting data values

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Database Approach to Data Processing

Guide to Oracle 10g 9

Database Systems (continued)

• Database administrator– Person responsible for installing, administering,

and maintaining the database

– Often called DBA

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Overview of Relational Databases

• Table– Matrix with columns and rows

• Columns – Represent different data fields

– Characteristics or attributes about entity

• Rows – Contain individual records

– Attributes about a specific instance of entity

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Overview of Relational Databases (continued)

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Overview of Relational Databases (continued)

• Entity– Object about which you want to store data

– Different tables store data about each different entity

• Relationships– Links that show how different records are related

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Overview of Relational Databases (continued)

• Key fields– Establish relationships among records in different

tables

– Main types of key fields• Primary

• Candidate

• Surrogate

• Foreign

• Composite

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Primary Keys

• Column in relational database table whose value must be unique for each row

• Serves to identify individual occurrence of entity• Every row must have a primary key• Cannot be NULL• NULL

– Value is absent or unknown

– No entry is made for that data element

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Candidate Keys

• Any column that could be used as the primary key• Should be a column that is unique for each record

and does not change

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Surrogate Keys

• Column created to be record’s primary key identifier

• Has no real relationship to row to which it is assigned other than to identify it uniquely

• Surrogate key values automatically generated using a sequence

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Foreign Keys

• Column in table that is a primary key in another table• Creates relationship between two tables• Value must exist in table where it is the primary key

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Composite Keys

• Unique key that is created by combining two or more columns

• Usually comprises fields that are primary keys in other tables

ORDER_ID PRODUCT_ID ORDER_QUANTITY

100 1 2

100 2 2

200 2 2

200 1 1

Composite Key

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Database Design

• Main tasks involved with design of database: – Developing entity-relationship (ER) model

– Normalizing database tables

Guide to Oracle 10g 20

Entity-Relationship Model

• Designed to help you identify which entities need to be included in database

• Composed of – Squares representing entities– Lines representing relationships

• Types of relationships:– One to one (1:1)– One to many (1:M)– Many to many (N:M)

Guide to Oracle 10g 21

Entity-Relationship Model (continued)

• One to one (1:1)– Each occurrence of a specific entity is found only

once in each set of data

– Rare in relational databases

• One to many (1:M)– Instance can only appear once in one entity, but

one or more times in the other entity

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Entity-Relationship Model (continued)

• Many to many (N:M)– Instance can occur multiple times in each entity

– Cannot be represented in physical database

– Broken down into series of two or more 1:M relationships through use of linking table in process of normalization

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Normalization

• Step-by-step process used to determine which data elements should be stored in which tables

• Purpose– Eliminate data redundancy

• Several levels of normalization– Forms

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Normalization (continued)

• Unnormalized data – Does not have a primary key identified

– Contains repeating groups

• First normal form (1NF)– Repeating groups removed

– Primary key field identified

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Example of Unnormalized Data

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Normalization (continued)

• Second normal form (2NF)– In 1NF

– No partial dependencies

• Partial dependency– Fields within the table are dependent only on part

of the primary key

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Normalization (continued)

• Basic procedure for identifying partial dependency:– Look at each field that is not part of the composite

primary key

– Make certain you are required to have both parts of the composite field to determine the value of the data element

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Normalization (continued)

• Third normal form (3NF)– In 2NF

– No transitive dependencies

• Transitive dependency – Field is dependent on another field within the table

that is not the primary key field

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Database Systems

• Consists of– DBMS

• Manages physical storage and data retrieval

– Database applications• Provide interface that allows users to interact with

database

• Server – Computer that shares resources with other

computers

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Database Systems (continued)

• Server process – Program that listens for requests for resources from

clients

– Responds to requests

• Client– Program that requests and uses server resources

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Personal Database Management Systems

• DBMS and database applications run on same workstation

• Appear to user as a single integrated application• Used primarily for creating single-user database

applications• Can also be used for some multiuser applications• Should be used only for applications that are not

mission critical

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Personal Database Management Systems (continued)

• Microsoft Access– Stores all data for database in a single file with

an .mdb extension

– Database administrator stores .mdb file on a central file server

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Using a Personal Database for a Multiuser Application

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Personal Database Management Systems (continued)

• Transaction processing – Grouping related database changes into units of

work that must either all succeed or all fail

– DBMS can use the transaction log to reverse—or roll back—the changes

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Client/Server Database Management Systems

• DBMS server process runs on one workstation• Database applications run on separate client

workstations across network• Server sends only requested data back to client

rather than entire database

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Client/Server Database Architecture

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Client/Server Database Management Systems (continued)

• Generate less network traffic than personal databases

• Extra features to minimize chance of failure• Powerful recovery mechanisms that often operate

automatically• Maintain file-based transaction log on database

server

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Client/Server Database Management Systems (continued)

• Preferred for– Database applications that retrieve and manipulate

small amounts of data from databases containing large numbers of records

– Mission-critical applications

– Web-based database applications that require increased security and fault tolerance

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The Oracle 10g Client/Server Database

• Oracle 10g– Latest release of Oracle Corporation’s relational

database– Client/server database

• Server side– DBMS server process

• Oracle Net– Utility that enables network communication

between client and server

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Client/Server Architecture for Oracle 10g DBMS

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The Oracle 10g Client/Server Database (continued)

• Oracle Application Server– Used to create World Wide Web pages that allow

users to access Oracle databases

• Oracle client products:– SQL*Plus

– Oracle 10g Developer Suite

– Enterprise Manager

Guide to Oracle 10g 42

The Database Cases

• Fictional organizations:– Clearwater Traders

– Northwoods University

• Design principles:– Convert all tables to third normal form

– Include primary key as foreign key in table on “many” side of relationship

– Specify data type for each column

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The Clearwater Traders Sales Order Database

• Clothing and sporting goods through mail-order catalogs

• Wants to begin accepting orders using Web site• Required data consists of information for:

– Customers

– Orders

– Items

– Shipments

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The Clearwater Traders Sales Order Database (continued)

• Tables:– CUSTOMER

– ORDER_SOURCE

– ORDERS

– CATEGORY

– ITEM

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The Clearwater Traders Sales Order Database (continued)

• Tables (continued): :– ORDER_LINE

– SHIPMENT

– INVENTORY

– SHIPMENT_LINE

– COLOR

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Visual Representation of the Clearwater Traders Database

Guide to Oracle 10g 47

The Northwoods University Student Registration Database

• Student registration system• Data items consist of information about:

– Students

– Courses

– Instructors

– Student Enrollment

Guide to Oracle 10g 48

The Northwoods University Student Registration Database (continued)

• Tables:– LOCATION

– FACULTY

– STUDENT

– TERM

– COURSE

– COURSE_SECTION

– ENROLLMENT

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Visual Representation of the Northwoods University Database

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Summary

• Relational databases – Store data in tabular format

– Create relationships that link related data using key columns

• Primary key– Column that uniquely identifies specific record

• Foreign key – Creates relationship between two tables

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Summary (continued)

• Entity-relationship (ER) model – Used to describe types of relationships between

entities

• Normalization process – Used to determine which fields belong in which

tables

• Database system consists of – DBMS

– Database applications

Guide to Oracle 10g 52

Summary (continued)

• Client/server databases divide database into – Server process that runs on network server

– User application processes that run on individual client workstations

• Oracle 10g is a client/server database