Relating to Modern Databases
You have spent the last two hours getting a good introduction to the concept of "database." Hour 1, "What Is a Database?" reviewed some of the basics, such as why we have databases, ways in which databases are used, and how the large volumes of data are used and refined to help those in business make informed decisions. In Hour 2, "History and Evolution of Database Environments," you learned some of the different ways in which the handling of data has evolved from a data management perspective and the hardware architectures typically used to handle databases. Now that the foundation has been covered and you have a clearer concept of what a database is, it's time to look at some reality-based systems that use databases. In this hour, you will look at a few common examples of database usage and take a closer look at the way data is managed and stored within these databases.
The first example studies the process of purchasing from a popular Web retailer. Another takes a look at a practice that has had some share of controversyfile content sharing. Other examples may not appear to be as technology intensive as the first two, but as you take a closer look at getting a prescription filled and using an ATM (automated teller machine), you will see that databases play an integral part in those systems as well.
By the end of this hour, you should have a clearer understanding of where databases are used in normal daily activities and transactions, from shopping to banking to retail purchases, whether in a conventional bricks-and-mortar store location or on the Net.
Using the Internet
The proliferation of home-based computing, along with Internet access from work locations, has fueled an exponential growth of World Wide Web (WWW) sites and users. As this growth occurs, the number of retailers offering their goods and services via the Internet has skyrocketed. The types of companies with Internet presence represent a wide variety of domestic and international business entities. Familiar brick-and-mortar retailers, although well established and usually well financed, have not necessarily dominated the Internet retail landscape. Some of the most frequently purchased items on the Net include books, videos, and CDs. Amazon.com, a well-known company dominating this market sector, is the subject of the first example. The Internet is becoming a thriving environment for modern databases.
The intent of this hour is to identify common real-world databases to which we all can relate. In subsequent hours, we will discuss in more detail the elements that comprise databases such as those discussed in this hour.
Making a Book Purchase
Our first example involves a common real-world database that many of us have used; Amazon.com. If you have never visited the Amazon.com Web site, you can reach it by entering http://www.amazon.com into the location bar of your browser and clicking Go. Figure 3.1 shows an example of the Amazon.com home page.
Figure 3.1 Amazon.com home page.
Because the number of items in the Amazon.com database is so large, broad product categories are presented on the left side of the Web page. Choosing a product category helps to narrow the number of items within the database that will eventually be viewed. For this example, select the Books category. Then you are presented with another list of products, all book categories. Figure 3.2 shows how you can drill down into the Books category.
Figure 3.2 Limiting your interest to books.
As you survey the content on the second page, you can begin to get a feel for the extensive database that must be in use behind the scenes at Amazon.com.
The right side of the page shows the bestsellers based on an hourly recomputation. To calculate this bestseller list, a sales history database (probably tracking sales transactions by customer number and by ISBN) must be searched. The top 10 selling ISBN numbers are returned. These top-selling ISBN numbers are then used to retrieve the book titles, authors, and other book information that is presented on the Web page in tabular format.
The left side of the page has a column of book categories. This implies that the database of books available is still too large to simply scroll through all the selections. The Web site enables you to further limit your search of the book database by category of books. In this example, when you pick the Computer and Internet category, a subsequent page is displayed, enabling you to continue to "drill down." After you have narrowed the selection of books from the database to a small electronic "shelf" area, you can browse the shelf for the book of your choice.
As an alternative, the entire database of books can be searched from the home page. Indexing of the database allows the user to quickly identify books of interest by author, by title, or by topic.
The database also has editor reviews, customer reviews, inventory availability data, and pricing information for each book.
If you find the book you want and decide to make the purchase, a customer database record is retrieved to find the customer name, address, city, state, zip, and phone number. Most often, when making an online purchase, your email address is also requested so that order confirmation and shipping advice information can be conveyed to you electronically. If the information is not found in the database, a series of screens will be presented for you to provide the needed data to populate your customer record.
Now that Amazon.com can identify you as the customer, and you have selected the books you want to buy, it's time to take your electronic shopping cart to the checkout line. This process fills some database table(s) with sales information. Beginning with your customer number, Amazon.com needs to determine your shipping address. If you are a repeat customer, your previously used shipping address is retrieved from the database and displayed for you. If this isn't the address to which the order is to be shipped, new Ship To address information must be entered and tracked in the database specifically related to this order. Hour 2 discussed the concept of a relational model database. Your trip to Amazon.com builds relational database entries about you and your order. Figure 3.3 shows the page where this data is stored in the database.
Figure 3.3 Shipping data for your order.
After Amazon.com knows where the order is going to be shipped, the method of payment must be specified. The ordering system asks you to indicate which credit card you will be using. After indicating card choice, the credit card number and expiration date is entered along with the exact cardholder name. The credit card information you provide is then verified by using another database to ensure the card's validity. Figure 3.4 illustrates the payment process.
Figure 3.4 Paying for your order.
After the credit card information is provided and verified, the Amazon.com system submits your credit card information along with your order's total value to a credit card servicing authority. The credit card company validates your card number against its database, checks the credit limit and available credit amount, and determines whether the sale can be approved. After the credit card company records your purchase details into its database, the sale authorization number is returned to Amazon.com where it is recorded into your sales transaction record. Now Amazon.com has recorded several data items into your customer record: billing data, shipping data, book ISBN and quantities, credit card data, and purchase authorization number.
The sale transaction data is then used in several ways behind the scenes. Minimally, the sale transaction has to be used to update the inventory on the books and items that have been shipped. This triggers activity for the purchasing group, which must reference the supplier database for minimum order quantity, shipping costs, and book costs to determine an economic order quantity and place an order for inventory replenishment. This purchase order database is used to check inventory receipts at the time the books are received into their warehouse from the publisher or distributor.
Finally, the sale transaction will be used periodically in a forecasting model database to determine buying trends, seasonality factors, and beta factors. These factors are all determined by evaluating the sales transaction database over a long period of time. The purchasing and inventory control groups within a company will use these predictive forecasting quantities to adjust inventory levels and inventory dollar investments to optimize a minimization of inventory dollars and maximization of customer serviceability.
The database at Amazon.com also displays other book titles in which you may have an interest. The database has association rules, like identifiable trends, where users interested in book A have demonstrated an interest in books B and C and also have shown an interest in books from author D. This data, more complex in nature than simply a list of books in the database, is derived by evaluating large volumes of historical data by user, by author, or by title. Figure 3.5 shows the results of the historical data for trends.
Figure 3.5 Suggested buying trends.
Downloading Information from the Internet
A wide variety of file content sites on the Net enable you to download anything from white papers and articles of interest, screensavers, software packages, games, movies, and music. The most publicized site may be Napster.com, with all the legal battles and court injunctions, but the site you will look at is called Kazaa.com. Kazaa.com provides free software to search its databases and to download files. If you have not visited the site, enter http://www.kazaa.com into your browser and click Go. Figure 3.6 shows an example of the Kazaa.com home page.
Figure 3.6 Kazaa.com home page.
The navigational aids on this site are similar to those at Amazon.com. The database of available music is too large for a user to browse through the available titles, so the site enables you to begin your search within a category, such as Top 40, Jazz, Country, or Rock/Pop. These categories are essentially subsets of all song titles in the database. The database can also be segmented using other qualifiers, such as by artist or by album.
When a particular file is identified to download, another database is searched to determine which connected users have your file available for download. You will typically have a chance to view the sources of your file, connection speeds, and file size. After the source is picked, a peer-to-peer transfer from the source PC to your PC occurs. Figure 3.7 shows all the peers identified for your file download.
Figure 3.7 Sources for your file.
If you are after a particular type of file, you can narrow your search of the database to include only one type. Kazaa.com supports searches for audio, video, images, documents, and software.
Many times, you can find other files from the database that have something in common with a file you have already downloaded. For instance, you can find files from the same artist or author (audio, image, documents), from the same album (audio), and from the same publisher (video, software) .