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A Guide to Oracle9i 1
Client/Server Databases and
the Oracle9iRelationalDatabase
Chapter 1
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Objectives Develop an understanding of the purpose of database systems
Become familiar with the structure of a relational database and
review relational database concepts and terms
Explore the differences between personal databases andclient/server databases
Learn about the Clearwater Traders sales order database, theNorthwoods University student registration database, and theSoftware Experts project management database
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Before Databases
Information was kept in files:
Each field describes one piece of information about student
Fields are separated by commas
A record is a collection of related fields
Each record is a separate line
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Problems with Files
Proliferation of
data management
programs to dealwith different file
formats
Redundant data
stored in files
Data files may
contain
inconsistent data
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Database Approach Database stores all organizational data in a central location
Good database design eliminates redundant data to reduce the
possibility of inconsistent data
Single application called the database management system
(DBMS) performs all routine data handling operations
Database administrator(DBA): person responsible for
installing, administering, and maintaining the database
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Early Databases
Hierarchical Structure
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Relational Databases
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Relational Database Terms Entity: an object about which you want to store data
Relationships: links that show how different recordsare related
Key Fields: establish relationships among records indifferent tables
Five main types of key fields: primary keys
candidate keys surrogate keys
foreign keys
composite keys
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Primary Keys
Primary key Value must be unique for each record
Serves to identify the record
Present in every record
Cant be NULL
Should be numeric
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Candidate Keys
Candidate key Any field that could be used as the primary key
Should be a unique, unchanging numeric field
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Surrogate Keys Surrogate key: created to be the records primary key identifier when
no suitable primary key exists
Surrogate key has no real relationship to the record to which it isassigned, other than to identify the record uniquely
Developers configure the database to generate surrogate key valuesautomatically
In an Oracle database, you can automatically generate surrogate keyvalues using a sequence
Surrogate keys are always numerical fields, because the databasegenerates surrogate key values automatically by incrementing theprevious value by one
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Foreign Keys Foreign key: a field in a table that is a primary key in another table
Foreign key creates a relationship between the two tables
Foreign key value must exist in the table where it is a primary key
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Composite Keys
Composite key: a unique key that you create by
combining two or more fields
Usually comprised of fields that are primary keys in
other tables
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Personal Database
Management Systems DBMS and database applications run on the same workstation and
appear to the user as a single integrated application
Personal databases used primarily for creating single-user databaseapplications
Support small multiuser database applications by storing the database
application files on a file server instead of on a single users workstation
and then transmitting the files or the parts of files containing the desired
data to various users across a network
Database developers should use a personal database only for non-
mission-critical applications
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Client/Server Database
Management Systems Client/server database
Takes advantage of distributed processing and networked
computers by distributing processing across multiple computers
DBMS server process runs on one workstation, and the databaseapplications run on separate client workstations across the network
Preferred for database applications that retrieve and manipulate
small amounts of data from databases containing large numbers of
records because they minimize network traffic and improve
response times
Organizations generally use a client/server database if the
database will have more than 10 simultaneous users and if the
database is mission critical
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Client/Server Database Architecture
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The Oracle9iClient/Server Database
Oracle9iis the latest release of Oracle Corporations relationaldatabase
All Oracle server- and client-side programs use Oracle Net, a
utility that enables the network communication between the
client and the server
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Client-Side Utilities SQL*Plus
for creating and testing command-line SQL queries and executingPL/SQL procedural programs
Oracle9iDeveloper Suite
for developing database applications including the followingDeveloper tools:
Forms Builder
for creating custom user applications
Reports Builder
for creating reports for displaying, printing, and distributing
summary data Enterprise Manager
for performing database administration tasks such as creating newuser accounts and configuring how the DBMS stores and managesdata
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Design Principles To avoid creating tables that contain redundant data, group
related items that describe a single entity together in a common
table
Do not create tables that duplicate values many times in
different rows
When creating a database and inserting data values, you must
specify the data type for each column
Recall that primary key fields should use a number data type to
avoid typographical, punctuation, and case variation errors
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The Clearwater Traders
Sales Order Database
Clearwater Traders
Markets a line of clothing and sporting goods via mail-order
catalogs
Accepts customer orders via telephone, mail, and fax
Wants to begin accepting orders using its Web site
Has decided to offer 24-hour customer order service
Existing microcomputer-based database system cannot handle
current transaction volume Managers concerned that the current database does not have
the failure-handling and recovery capabilities needed for an
ordering system that cannot tolerate failures or downtime
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Clearwater Traders Data
Requirements Customer name, address, daytime and evening telephone numbers,
user names, and passwords
Order date, payment method (check or credit card), order source(catalog description or Web site), and associated item numbers, sizes,colors, and quantities ordered
Item descriptions and photo images, as well as item categories(womens clothing, outdoor gear, and so on), prices, and quantities onhand. Many clothing items are available in multiple sizes and colors.
Sometimes the same item has different prices depending on the itemsize
Information about incoming product shipments
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Clearwater Traders
Table Relationships
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The Northwoods University
Student Registration Database
Northwoods University
Decided to replace its aging mainframe-based
student registration system with a more modernclient/server database system
School officials want students to be able to retrieve
course availability information, register for courses,and print transcripts using personal computers
located in the student computer labs
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The Northwoods University
Student Registration Database (cont) Faculty members must be able to retrieve student
course lists, drop and add students, and record
course grades
Faculty members must also be able to view records
for the students they advise
Security is a prime concern, so student and course
records must be protected by password access
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Northwoods University
Data Requirements Student name, address, telephone number, class (freshman,
sophomore, junior, or senior), date of birth, PIN (personal
identification number), and advisor ID
Course call number (such as MIS 101), course name, credits,
location, duration, maximum enrollment, instructor, and term
offered
Instructor name, office location, telephone number, rank, andPIN
Student enrollment and grade information
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Northwoods University
Table Relationships
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The Software Experts Project
Management DatabaseSoftware Experts Consulting firm that creates custom software applications
Managers determine the number and the skill sets of the consultantsthat a given project requires
Managers locate available consultants with the necessary skills
One consultant is named project manager
When completed, the project manager evaluates all the otherconsultants and all the consultants evaluate the project manager
A project can be subdivided into multiple subprojects
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Software Experts Requirements
Consultant information, including name, address, city,
state, ZIP code, phone number, and e-mail address
Descriptions of consultant skills
Client information, including the client name, client contact
name, and contact phone number
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Software Experts Requirements
Project information, including the project name, the client
associated with the project, associated subprojects, the
project manager, and required skill sets
Dates that a consultant started and finished working on a
specific project and total days that the consultant spent
working on the project
Consultant evaluation information, including the date theevaluation was completed, who performed the evaluation,
and the evaluation score and comments
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Software Experts Table
Relationships
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Summary
A database stores all organizational data in a central location
Database management system (DBMS) provides a central set
of common functions for managing a database, including
Inserting
Updating
Retrieving
Deleting data values
Most modern databases are relational databases
Store data in a tabular format
Columns represent different data fields
Rows contain individual data records
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Summary
In a relational database
Data about different entities is stored in separate tables
You create relationships that link related data using key
fields
A database system consists of
DBMS: manages the physical data storage
Database applications: provide the user interface to the
database
Many database systems use a client/server architecture
DBMS runs as a server process
Database applications run as client processes
