Transcript Database Systems: Design, Implementation, and Management

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Chapter 15
Web Database Development
Database Systems: Design, Implementation, and
Management, Fifth Edition, Rob and Coronel
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In this chapter, you will learn:
• How Internet databases are typically used
• About the architecture of Web-to-database
middleware
• How Web-to-database middleware (ColdFusion) is
used to integrate databases with the Internet
• What special considerations govern Web
database development
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Web Database Connectivity
• Allows rapid response to competitive pressures
– New services
– New products
• Customer support enhanced
• Fast effective information dissemination
– Universal access
– Local
– Around the globe
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Typical Uses of Internet
Table 15.2
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Characteristics/Benefits
of Internet Technology
• Hardware & software independence
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Cost savings
Uses existing equipment
Platform independence and portability
No need for multiple platform development
• Common simple user interface
– Reduced training
– Reduced support
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Characteristics/Benefits
of Internet Technology (con’t.)
• Location Independence
– Global access through Internet
– Reduced costs for dedicated connections
• Rapid development at manageable costs
– Development tools
– Low entry costs
– Available software & access tools
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Web-to-Database Middleware
• Server-side extension
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Interacts directly with Web server
Handles specific requests
Also known as Web-to-database middleware
Examples
• ColdFusion
• CGI
• API
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Web-to-Database Middleware
Figure 15.1
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Web Server Interfaces
• Common Gateway Interface (CGI)
– Uses script files to connect to database
– Perl, C++, VB
• Application Programming Interface (API)
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Newer and more efficient
Uses DLLs
Memory resident and faster
Well known APIs
• Netscape (NSAPI)
• Internet Server API from Microsoft (ISAPI)
• WebSite API from O’Reilly (WSAPI)
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API and CGI Web Server Interfaces
Figure 15.2
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Web-to-Database Middleware
Connection Methods
• Native SQL access middleware
• Use services of Open Database Connectivity
(ODBC)
• Use Object Linking and Embedding Database
(OLE DB) interface with Windows
• ODBC most common
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ODBC to Access Databases
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel
Figure 15.3
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Web-to-Database Middleware Uses
ODBC to Access Databases
Figure 15.4
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Web Browser
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Located on the client computer
End user Web interface
Interprets HTML code received from Web server
Presents page components in a standard way
Client-side extensions
– Plug-ins
– Java and JavaScript
– ActiveX and VBScript
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ColdFusion
• Web application server
• Uses
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Connect and query database from Web page
Present database data in a Web page
Create dynamic Web search pages
Create Web pages to insert, update, and delete
data
Define required and optional relationships
Define required and optional form fields
Enforce referential integrity in form fields
Use simple and nested queries to represent
business rules
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How ColdFusion Works
Figure 15.5
Database Systems: Design, Implementation, & Management,
5th
Edition, Rob & Coronel
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How ColdFusion Works
• Server-side markup language
– HTML extensions
– ColdFusion Markup Language (CFML)
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Executed in interpreter mode
Contain HTML, CFML
May contain Java, JavaScript, or VBScript
Client browser requests .cfm page from Web
Server
– ColdFusion application server executes .cfm script
– Sends resulting output in HTML to Web Server
– Web server sends to client browser
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ColdFusion Tags
• CFQuery
– Queries a database
• CFOutput
– Displays data returned by query
• CFTable
– Displays data in Tabular format
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ColdFusion Dynamic Query
• Create script to generate form with criteria used
in database search
• Create script to execute query and display results
– Uses ColdFusion tags
– Uses HTML
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The Web as a Stateless System
• Web server does not know status of any client
at any given time
• Request-reply model of communication
• Browser concerned only with current page
• Data processing requires additional software
– Java, JavaScript, VBScript
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INSERTs and UPDATEs with
ColdFusion
• CFINSERT Tag
– Adds records to database
– Parameters
• DATASOURCE
• TABLENAME
• CFUPDATE Tag
– Updates selected database contents
– Parameters
• DATASOURCE
• TABLENAME
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DELETEs with ColdFusion
• CFQUERY Tag
– Uses SQL DELETE Statement
– Parameters
• DATASOURCE
• TABLENAME
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Internet Database: Special
Considerations
• Involve more than just database-enabled Web
applications
• Issues important to corporate databases
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Data security
Transaction management
Client-side data validation
Operational and management challenges
• Database applications development most
affected by Internet
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Supported Data Types
• Integrated data from multiple sources
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Word-processor documents
Pictures
Sounds
Movies
Methods for storing and extracting data objects
Overhead created by storage
Client browser support of object being accessed
Size of database considering multimedia and
other data
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Data Security
• Web Server Level
– Secure transactions using encryption
– TCP/IP protocol level
– Firewalls
• RMDBS Vendors
– Login authentication
– Restrict access to particular SQL commands
• Web-to-database middleware
– End user restrictions
– Designer created algorithms
• Must support e-commerce applications
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Transaction Management
• Concept is foreign to Web
• Dilemma created by request-reply model
– Web cannot maintain open line between client and
database
– Recovery requires client maintain open
communications
• Designers must ensure proper transaction
management support at database server level
• ColdFusion uses CFTRANSACTION tag for
transaction management support
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Denormalization
• Web forms
– Cannot use multiple data entry lines
– 1:M relationships problematic
• Solutions
– Web programming languages
– Java, JavaScript, VBScript
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