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Introduction to Databases for Web Developers
Chains of Communication  
As you recall from Part One, a Web Database follows the client-server database model. A Database Engine sits on some central computer somewhere and serves data to multiple web-based clients (perhaps lots of customers using Netscape Navigator).

Because we are dealing with web-based clients however, we must also have a Web Server that handles requests from web-browsers and then forwards them to the Database. Likewise, the web server will wait for the database to respond and then pass on that response to the waiting web browsers. The whole interaction is much simpler as a picture.

(Note that since you are a web developer, I am assuming that you understand the interaction between web browsers and web servers. If you don't understand this, or if you need a refresher, check out Web Programming 101 at WDVL!)

[Web Browser-Web Server-Database]

Of course, the problem with the above model is that it does not exactly tell the whole story. Actually, though Web Servers are built to talk to Web Browsers, they are not built to talk to Databases. Thus, in order for the Web Server to talk to a Database, it requires a helper (sometimes called Middle Ware).

The most basic type of Middle Ware is a CGI script that is written to translate requests from the Web Server to a format that the Database can understand, and to translate Database responses into something the Web Server can send back out to the Web Browser and that the person using the web browser can understand.

[Web Browser-Web Server-CGI Script-Database]

The CGI Script will be responsible for understanding what the Web Server is saying and will also be responsible for knowing how to talk to the Database. This type of CGI script is seriously multilingual!

[Web Browser-Web Server-CGI Script-Database]

Of course, the CGI script can be written in any computer programming language and can use all sorts of inventive or proprietary methods to talk to the Database.

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