Introduction

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When I wrote MySQL for New Riders a year and a half ago, I wondered whether it would receive much of a response, because it wasn t apparent whether the MySQL community was very sizable. I should have known better! MySQL is a very good database, it s easy to use, it s fast, and it s free all characteristics that help make it deservedly more popular each day. And it s clear now that its users are interested in reading more about it. Consequently, after publishing MySQL, the folks at New Riders began to consider how the database community could be served by another MySQL-based title. As we discussed ideas, one that quickly came to mind was the need for substantial coverage on the topic of using MySQL in tandem with Perl and its DBI module for writing Web-based database scripts. This combination is quite widely used, but, oddly enough, only sporadically documented. The result? Many people who see how popular MySQL and Perl are in Web environments decide to try them out, but find themselves without a source that deals at length specifically with these tools.

This book changes that. It contains extensive practical material that will enable you to use MySQL and Perl to bring your Web site to life. It helps you write applications that interact with your visitors and applications that provide dynamic content, freeing you from being tied to static pages that must be updated by hand. The approach used here is based on the belief that learning from examples is one of the most effective ways to gain knowledge and experience. You ll find functional applications that you can modify to suit your own purposes. What you won t find is page after page of program listings with little explanation of what s going on. Examples are more meaningful when you understand them, so each application is fully described so that you know not only what it does, but also how and why.This approach emphasizes the following key features:

• Practicality. I assume you re interested in working code that does real stuff, so that s what you ll get here. But we ll also discuss the reasons why you do things a certain way, because such understanding will allow you to adapt the material to many more contexts than would any rote-learning approach. We ll discuss the principles that go into designing and implementing the applications, to provide knowledge that will help you modify them more readily or design new ones based on similar principles. If, as is common for Perl, there s more than one way to do it and multiple techniques bear consideration, we ll discuss and compare them.

• Accessibility. The material here is technical, but not impenetrable. I believe it s possible to present content and substance in a practical way that is also easy to understand and use.

• Generality. As we develop a particular application to perform a specific task, I ll point out other types of problems that can be addressed with the general techniques used in the application. That way you can look beyond the code to see how it might be adapted to other purposes some of which might be of more interest to you than the immediate purpose for which the application is written here.

You ll notice that applications in this book sometimes develop in fits and starts. I ll show one way to do something, and then point out a shortcoming and show how to do it better occasionally several times. This isn t always the most direct approach, but it provides more latitude to discuss alternatives.

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