Connecting Databases to the Web
Static v. Dynamic Web Applications
 | Static - data is in HTML pages, pages must be rebuilt and deployed for updates. |
| Dynamic - data is stored in database, application builds the web pages as needed. |
Types of Applications
| Search Engines |
| E-commerce |
| Large scale information delivery |
| Examples: http://www.amazon.com, http://www.altavista.com |
Tools for Creating Web Database Applications
| Can be as simple as text editor and appropriate web server configuration. |
| Tools are often server-dependent |
| Visual InterDev - Microsoft interactive Web development tool |
| Oracle 8i - web database integration tools |
| Allaire HomeSite and Microsoft FrontPage- can be used to create server/client side projects |
| Drumbeat |
Techniques for Connecting to Databases
| ODBC |
| OLE/DB |
| Other techniques (depends on platform and database). |
ODBC
|  Open
Database Connectivity (ODBC) technology provides a common interface for
accessing heterogeneous SQL databases. |
| ODBC is based on Structured Query Language (SQL) as a standard for accessing data. This interface provides maximum interoperability: a single application can access different SQL Database Management Systems (DBMS) through a common set of code. |
| It enables a developer to build and distribute a client/server application without targeting a specific DBMS. |
|  Database
drivers are then added to link the application to the user's choice of DBMS. |
| ODBC Applications are not tied to a proprietary vendor API. |
OLEDB Technology
| Microsoft specification for integrating databases with applications (including the web). |
| It is built on Microsoft COM and is seen as both a complement and a replacement for ODBC. |
| Intended to be faster, more efficient, easier to maintain and use. |
| Includes direct connectivity (C++, J++) and connectivity via ODBC. |
Web Architecture - Based on Standards
Browser
| HTML standards |
| Vendor implementations |
TCP/IP
| Internet v. Intranet |
| Bandwidth |
HTTP/HTTPS
| Standards for implementation |
| Platforms - UNIX, NT most common |
| Implementations - Apache, IIS, Netscape |
CGI
| Standard for HTTP communication with environment. |
Web/Database Architecture
Two Tier Model
Three Tier Model (Separate Database Server)
Web Forms and CGI (Common Gateway Interface)
Web Form - displays/presents the data.
|
Basic set of controls for an interactive interface |
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Text box, Radio Button, Check Box, Button, List Box |
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Form is directed to a web application/page. |
Post/Get - sends data from the browser to the server.
|
Post - sends as part of the Request data stream (stdin/out) |
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Get - sends as part of the URL (www.acme.com/appname?param=value¶m2=value) |
CGI Operation
|
Depends on a programming interface between application and web server. |
|
Key aspects include input/output (data) & server operations |
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Moves data between the web server and the server-database application. |
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Provides server/environment information to application |
|
Can be used to maintain state information |
Database Connections via Object Technology (for Microsoft anyway)
|
ActiveX Data Objects = ADO |
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Integrates with ASP, Perl, Java, and other web server technologies. |
|
Components that allow you to connect to and access a database. |
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Key objects: Connection, Recordset, Error |
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Connection - identifies the database, establishes a link (“database connection”). Is used to insert, update, delete data from tables. |
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Recordset - holds the data – handles the product of a select statement. |
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Error – identifies and tracks errors during database interactions. |