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Introduction to Databases for Web Developers
The DBI Module  
The DBI Module is an incredibly useful tool because it abstracts away the need to learn how to communicate with every type of database out there. Consider what a pain it would be if you had to write a CGI script for every proprietary database engine.

Now imagine how much extra work you would have if the management decided to change database vendors on you after you had already written your code!

[No abstractions to Database]

What the DBI module does for you is to provide a single interface to send SQL commands to any proprietary database. Essentially, you write all your code to a generic standard, and move it from database to database without having to re-code your application.

The secret to the DBI module is the extensive library of DBD (Database Dependent) modules that come with the standard distribution of Perl 5. These DBD modules provide the code that hooks up DBI to a proprietary database driver.

Of course, since these DBD modules are already written for almost any Database you would consider using, you needn't do any of that hard work. All you need to worry about is satisfying the requirements of the DBI interface. Everything else is handled behind the scenes!

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

It looks pretty complex but believe me, it isn't. And it makes your life as a programmer incredibly easy. That is, although the communication takes place through so many actors, you, as the programmer need not bother with the details of that communication. You talk to the DBI module, and the DBI module handles the multitude of proprietary database blue meanies by itself.

Fortunately, dozens of great module writers have done all that hard work for you. You'll see just how easy it is when we start going over code!

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