I’m sure you are quite familiar with HTML pages or web-pages, as they are popularly called. These are pages stored on the web server, which you can download into your browser by typing in the website address or by clicking on a hyperlink that points to that page. This seems rather easy. So we’re not looking at simple web pages or websites. In this article, we would be looking at something far more complex—namely, dynamic web pages and websites!

The Need for Databases
Let me start off with a story.

Whichever city or town you live in, I’m sure you have a favorite sabzi-wala, who comes around to your house every day with his cart piled up with greenish potatoes, stale onions, sorry-looking peas, and beans that may have been fresh a week ago. However, that is not the point. The point is that he sells you something every day. And for example’s sake let’s call him Haribhai. Thanks to the online medium, your good old honest sabzi-wala need not visit you any more. Why? Because
he’s launched his own website, www.sabziwala.com. And, his young nephew, who is under training to become a proud sabziwala in his own right some day, delivers whatever you order on the Internet.

Haribhai has engaged a leading American multinational (headquartered in Boston, Massachusetts) to create his e-commerce software, which is naturally full of HTML pages, each page containing vegetable listings, package sizes, prices for each, time to deliver, and so on and so forth.

Suddenly one day there is a rumor that the transporters of the area may go on strike. And Haribhai realizes with that he can now charge twice as much for the same old stale vegetables. But when he goes to the MNC, to ask if they could modify the rates in his website, he is in for a big shock. "Sorry, sir, but we’ll have to change the HTML pages. And that means you need our programmers all over again. And that will mean an additional sum of about $10,000. But since you are a valued customer and a major account for us, we’ll cut it down to just $8,000," came the reply.

Haribhai is shattered. How can he possibly make up this money even if he charges three times the normal rate. And then he gets another terrible thought—tomorrow, when the rumor is squashed by the appropriate government official, he would have to bring the prices down again. So he would again need to go back to the multinational - $8,000 once again. And indeed every time he changed the price of his vegetables; the gainer would only be the software company!

Apart from feeling sorry for Haribhai, can we really offer a solution? Indeed, there has to be a solution, because the data that you put out on your HTML page needs to be changed at regular intervals. In fact, there are many software companies that have moved from HTML websites to dynamic websites, which use relational databases.

Dynamic and Static Sites
A database in the basic sense can be defined as a collection of data—obviously organized in some manner. And you can query this database to get whatever data you want. Databases are an essential component of any website today, and in fact of any computer-based application, whether on the Internet or otherwise. So let’s take a look at Haribhai’s vegetable database. Assuming he needs to store three pieces of information—name of the vegetable, size of packing, and price. The database would then be in the form of a table (See Table 1).

Notice that this table defines a "relationship" between name of vegetable, size of pack, and price of pack. Consequently it doesn’t take much imagination to see why such a database is called a relational database. In fact the table itself is often called a relation!

Now let’s see how we can query such a database. If we wanted to get the price of a half kilo pack of onions, we would give a command to the database which would look something like this: "Get the price of pack for the row where name of vegetable is ‘onion’, and size of pack is ‘0.5 Kilos’

And naturally, the result will be another table—this time a smaller one. And the result of the query is price of pack—Rs 20. Notice that the result of the query doesn’t need to give the first two entries (name of vegetable and size of pack). Because you know that anyway—after all you were the one who asked the question. It’s like an exam where the student doesn’t have to write down the entire question along with the answer—just the answer will do, as long as he writes down the question number.

This type of querying is usually done in a standardized language called SQL, which stands for structured query language. Obviously it is more formal than the simplified stuff I have been showing you, but the essence is the same. Now, Haribhai’s problem can be finally solved

Because now, whenever Haribhai needs to change prices, he doesn’t need to change the entire HTML page. He doesn’t need a programmer. Most of all, he certainly doesn’t need the Boston-based multinational. All he needs is someone who understands simple English, who can enter this data into the database every time it changes. In fact, his 12-year old niece who goes to an English Medium school could do the job.

Another advantage of having an improved website is that it gives you one more set of technical jargon that you can brag about, namely dynamic sites and static sites. A static website is one, which consists of HTML pages that are permanent and cannot be easilty modified or updated. Any changes in such a site require an entire re–programming of the HTML coding. Therefore such sites are useful in cased where infomation does not have to be changed very often.

On the other hand, dynamic sites are those where the web page is created dynamically—as in our example—through a database, instead of being permanently coded in HTML. As discussed, these sites are useful when some of the HTML pages need the flexible option of editing and upgrading a part or the entire data. In other words, these kind of websites can be called that database-driven sites as they are more maintainable than plain HTML websites, which are simply based on static HTML pages.

So, where does all this information that is constantly being updated get saved and stored? This data is resting on a separate server called the data server. The data server is generally connected to the web server through a LAN or local area network link (See Fig. 1).

Fig 1: The data server and web server are connected through a Lan link

At end of the day, Haribhai got a solution to his problem, and without burning a hole in his pocket! Needless to say, his website is a roaring sucess.

DHRUV NATH is a Professor at MDI, Gurgaon.