Doing Dynamic Data

A normal database server delivers query results to the user's terminal. Providing Web access requires one additional step: formatting the results in Hypertext Markup Language (HTML). From a browser, the user submits a uniform resource locator (URL) specifying either a script (to be executed on the server) or a file. For example, the following URL would request Microsoft's Internet Information Server (IIS) to execute a script: http://www.nstl.com/sample.idc . The results are returned directly to the server as H TML instead of being saved as files. Such HTML pages produced by script execution are called dynamic pages because their content can be different each time the script is executed. HTML pages stored in files are called static pages because their content doesn't change between requests unless an administrator or developer explicitly modifies the file.

Web database applications can use either static or dynamic pages. Any database programming tool can produce static pages by writing output to a text file with appropriate HTML formatting. Dynamic pages aren't so easy to produce. They require specialized applications that can accept requests from an Internet server, access a database, and return HTML directly.

Dynamic pages offer two capabilities not available in static pages. First, a script can query a database based on user-supplied selection criteria, which can differ each time. For example, the following URL requests the query.idc script to return only those record s where the variable "state" contains the value CA: http://www.nstl.com/query.idc?state=CA .

A second capability of dynamic pages is data entry. A user can submit a request for a script that performs an insert or update operation rather than a query. Here the script must recognize the variables included in the URL as data with which to update the database. Many browsers allow the display of forms, which are HTML pages where users can enter information into fields. When the user finishes entering data, the system translates the information into a URL with variables, similar to the above example.

For a URL to initiate script processing, the Internet server must execute another program, pass information to it, and get information back. The Common Gateway Interface (CGI) is an API, supporte d by virtually all Internet servers, that allows interaction between an Internet server and an application. Unfortunately, CGI is notoriously slow, so many Internet servers provide their own, more efficient APIs. Microsoft IIS supports Internet Server API (ISAPI); WebSite Professional supports WebSite API (WS-API); and Oracle Workgroup Server supports Web Request Broker (WRB). Most Internet-server database-access mechanisms use their own APIs, but Cold Fusion, used by WebSite Professional, is a CGI application.

---

OLE, Can You C...My Data Request

illustration_link (30 Kbytes)