Databases

When you visit Yahoo or Lycos and search for a specific website, you are using a database. A database is an organized set of information. Each item in the database is given "relational properties". For example, when you search Lycos for "basketball teams", the database searches through all of its stored websites that have a relational property of basketball teams. These relational properties may be handcoded into the database or special software tools can search the websites for the words "basketball teams". With either technique the database software will generate a list of websites and produce HTML code listing hotlinks to related sites. That HTML code is then downloaded to your machine and you see the search results. Similar database systems are used when you order something online, check for the best airline fare, or ask for a definition in an online dictionary.

To understand how web-based databases work, it is important to realize that databases have been around a long time, in computer years anyway. Databases have existed on stand alone computers since the 1950's. Companies used them to store and retrieve information that they would then print out. A database is used to store your student records at Park Center. When you or school personnel request a printout of current records, the database searchs and compiles the correct information. That database, is however, not connected to the World Wide Web. Since the late 1990's, many companies and institutions have realized the value of connecting their database information to the WWW. Northwest Airlines, for example, realizes that they can sell more airline tickets if they make it easy for you to search for the cheapest, most convenient flight to your destination.

How are databases connected to HTML documents? There are two basic ways of structuring a database connection: client-side or server-side.

Server-side database connectivity is the oldest and most popular method. The software for connecting to the database resides on the webserver. Usually the database is stored in a seperate computer. The users requests information(usually by filling out a form)and the request is sent in HTML to the web server. The database connection software(ASP, SQL, etc.) changes the request into the language of the database program(Access, FileMaker Pro, etc.). The database program then searches its files, returns the information to the web server to be changed back into HTML(usually DHTML) and downloaded to the user. The network overhead for this architecture is substantial. Server-side remains the most popular architecture, however because it works the same for almost all users because the user is just dealing with basic well-supported HTML.
Client-side connectivity uses a script(VBScript, Perl, Javascript, etc) loaded directly in the HTML document that allows the user to skip the middleman and deal directly with the database server. A negative is obviously less support as these scripting languages are not dealt with equally by all browsers. You may exclude some potential clients that can't even use your database. Recently, more client-side databases are using Java applets or ActiveX controls which reside on a webserver, but download with the HTML document and remain in the RAM of the users computer. These mini-programs can talk directly to the database server. Java and ActiveX are also not totally supported by all browsers but the use of them is increasing. Although most web databases use server-side architecture today, client-side uses are increasing.

So, what do you need if you want to set up a search engine or other database on your website? You will need a database program(Access, FilemakerPro), a database server, and database connectivity software either in the form of a downloaded script or a program residing on your webserver. Needless to say, most personal webpages do not have the resources to create databases. Most major companies, however, find a database system to be a great business tool. Of the Beyond HTML sections of this curriculum, databases are probably the hardest to quickly incorporate into your webpage. However, Jay Greenspan of Webmonkey believes he can teach you a functional, simple database with no expensive tools. You can read his tutorial at Webmonkey and decide for yourself.

Index

Frames