Chapter 5. User-Driven Querying

In this chapter, we build on the querying techniques discussed in Chapter 4 and complete our coverage of techniques that read data from web databases. We focus here on user-driven querying, in which the user provides data that controls the query process. To input parameters into the querying process, the user usually selects or types data into an HTML <form> environment, or clicks on links that request scripts.

We explain user-driven querying by introducing how to:

• Pass data from a web browser to a web server.

• Access user data in scripts.

• Secure interactive query systems.

• Query databases with user data.

• Produce one script that contains an HTML <form> and the code that outputs the query results. We call this a combined script.

• Develop results pages with previous page and next page links.

• Use five-step querying to produce components for user input.

Our case-study example in this chapter is the wine browsing component of the winestore. Similar to most user-driven modules, the wine browsing component has two subcomponents: first, the search bar allows the user to enter a type of wine as a criteria for a database query; and, second, the results pages show the user the wines that match the criteria entered in the search bar. The search bar is shown in Figure 5-1 at the base of the winestore search page, and the results of running the query are presented above it in a results page. The results pages allow the user to view the wines in pages of 12 wines each, move between results pages, and add wines to his shopping cart.

Figure 5-1. The winestore search bar and results page

The querying just described is a two-component user-driven querying process. A less common type of user-driven querying describes a query that doesn't produce output, but instead returns the user directly to the query input component. This one-component querying process is often used to add items to a shopping cart. We also explain one-component querying in this chapter.

Extended examples of user-driven querying can be found in Chapter 10 to Chapter 13.