This section describes situations in which the MySQL database system is useful. This will give you an idea of the kinds of things MySQL can do and the ways in which it can help you. If you don't need to be convinced about the usefulness of a database system?perhaps because you've already got a problem in mind and just want to find out how to put MySQL to work helping you solve it?you can proceed to the "A Sample Database" section later in this chapter.
A database system is essentially just a way to manage lists of information. The information can come from a variety of sources. For example, it can represent research data, business records, customer requests, sports statistics, sales reports, personal hobby information, personnel records, bug reports, or student grades. However, although database systems can deal with a wide range of information, you don't use such a system for its own sake. If a job is easy to do already, there's no reason to drag a database into it just to use one. A grocery list is a good example; you write down the items to get, cross them off as you do your shopping, and then throw the list away. It's highly unlikely that you'd use a database for this. Even if you have a palmtop computer, you'd probably keep track of a grocery list by using its notepad function rather than its database capabilities.
The power of a database system comes into play when the information you want to organize and manage becomes voluminous or complex and your records become more burdensome than you care to deal with by hand. Clearly this is the case for large corporations processing millions of transactions a day; a database is a necessity under such circumstances. But even small-scale operations involving a single person maintaining information of personal interest may require a database. It's not difficult to think of scenarios in which the use of a database can be beneficial because you needn't have huge amounts of information before that information becomes difficult to manage. Consider the following situations:
Your carpentry business has several employees. You need to maintain employee and payroll records so that you know whom you've paid and when, and you must summarize those records so that you can report earnings statements to the government for tax purposes. You also need to keep track of the jobs your company has been hired to do and which employees you've scheduled to work on each job.
You run a network of automobile parts warehouses and need to be able to tell which ones have any given part in their inventories so that you can fill customer orders.
As a toy seller, you're particularly subject to fad-dependent demand for items that you carry. You want to know what the current sales trajectory is for certain items so that you can estimate whether to increase inventory (for an item that's becoming more popular) or decrease it (so you're not stuck with a lot of stock for something that's no longer selling well).
That pile of research data you've been collecting over the course of many years needs to be analyzed for publication, lest the dictum "publish or perish" become the epitaph for your career. You want to boil down large amounts of raw data to generate summary information and to pull out selected subsets of observations for more detailed statistical analysis.
You're a popular speaker who travels the country to many types of assemblies, such as graduations, business meetings, civic organizations, and political conventions. You give so many addresses that it's difficult to remember what you've spoken on at each place you've been, so you'd like to maintain records of your past talks and use them to help you plan future engagements. If you return to a place where you've spoken before, you don't want to give a talk similar to one you've already delivered there, and a record of each speech would help you avoid repeats. You'd also like to note how well your talks are received. (Your address "Why I Love Cats" at the Metropolitan Kennel Club was something of a dud, and you don't want to make that mistake again the next time you're there.)
You're a teacher who needs to keep track of grades and attendance. Each time you give a quiz or a test, you record every student's grade. It's easy enough to write down scores in a gradebook, but using the scores later is a tedious chore. You'd rather avoid sorting the scores for each test to determine the grading curve, and you'd really rather not add up each student's scores when you determine final grades at the end of the grading period. Counting each student's absences is no fun, either.
The organization for which you are the secretary maintains a directory of members. (The organization could be anything?a professional society, a club, a repertory company, a symphony orchestra, or an athletic booster club.) You generate the directory in printed form each year for members, based on a word processor document that you edit as membership information changes. You're tired of maintaining the directory that way because it limits what you can do with it. It's difficult to sort the entries in different ways, and you can't easily select just certain parts of each entry (such as a list consisting only of names and phone numbers). Nor can you easily find a subset of members, such as those who need to renew their memberships soon?if you could, it would eliminate the job of looking through the entries each month to find those members who need to be sent renewal notices. Also, you'd really like to avoid doing all the directory editing yourself, but the society doesn't have much of a budget and hiring someone is out of the question. You've heard about the "paperless office" that's supposed to result from electronic record keeping, but you haven't seen any benefit from it. The membership records are electronic, but, ironically, aren't in a form that can be used easily for anything except generating paper by printing the directory!
These scenarios range from situations involving relatively small amounts to large amounts of information. They share the common characteristic of involving tasks that can be performed manually but that could be performed more efficiently by a database system.
What specific benefits should you expect to see from using a database system such as MySQL? It depends on your particular needs and requirements?and as illustrated by the preceding examples, those can vary quite a bit. Let's look at a type of situation that occurs frequently and so is fairly representative of database use. Database management systems are often employed to handle tasks such as those for which people use filing cabinets. Indeed, a database is like a big filing cabinet in some ways, but one with a built-in filing system. There are some important advantages of electronically maintained records over records maintained by hand. For example, if you work in an office setting in which client records are maintained, the following are some of the ways MySQL can help you in its filing system capacity:
Reduced record filing time . You don't have to look through drawers in cabinets to figure out where to add a new record. You just hand it to the filing system and let it put the record in the right place for you.
Reduced record retrieval time. When you're looking for records, you don't search through each one yourself to find the ones containing the information you want. Suppose you work in a dentist's office. If you want to send out reminders to all patients who haven't been in for their checkup in a while, you ask the filing system to find the appropriate records for you. Of course, you do this differently than if you were talking to another person to whom you'd say, "Please determine which patients haven't visited within the last 6 months." With a database, you utter a strange incantation:
SELECT last_name, first_name, last_visit FROM patient WHERE last_visit < DATE_SUB(CURDATE(),INTERVAL 6 MONTH);
That can be pretty intimidating if you've never seen anything like it before, but the prospect of getting results in a second or two rather than spending an hour shuffling through your records should be attractive. (In any case, you needn't worry. That odd-looking bit of gobbledygook won't look strange for long. In fact, you'll understand exactly what it means by the time you've finished this chapter.)
Flexible retrieval order. You needn't retrieve records according to the fixed order in which you store them (by patient's last name, for example). You can tell the filing system to pull out records sorted in any order you like?by last name, insurance company name, date of last visit, and so on.
Flexible output format. After you've found the records in which you're interested, there's no need to copy the information manually. You can let the filing system generate a list for you. Sometimes you might just print the information. Other times you might want to use it in another program. (For example, after you generate the list of patients who are overdue on their dental visits, you might feed this information into a word processor that prints out notices that you can send to those patients.) Or you might be interested only in summary information, such as a count of the selected records. You don't have to count them yourself; the filing system can generate the summary for you.
Simultaneous multiple-user access to records. With paper records, if two people want to look up a record at the same time, the second person must wait for the first one to put the record back. MySQL gives you multiple-user capability so that both can access the record simultaneously.
Remote access to and electronic transmission of records. Paper records require you to be where the records are located or for someone to make copies and send them to you. Electronic records open up the potential for remote access to the records or electronic transmission of them. If your dental group has associates in branch offices, those associates can access your records from their own locations. You don't need to send copies by courier. If someone who needs records doesn't have the same kind of database software you do but does have electronic mail, you can select the desired records and send their contents electronically.
If you've used database management systems before, you already know about the benefits just described, and you may be thinking about how to go beyond the usual "replace the filing cabinet" applications. The manner in which many organizations use a database in conjunction with a Web site is a good example. Suppose your company has an inventory database that is used by the service desk staff when customers call to find out whether you have an item in stock and how much it costs. That's a relatively traditional use for a database. However, if your company puts up a Web site for customers to visit, you can provide an additional service?a search page that allows customers to determine item pricing and availability. This gives customers the information they want, and the way you provide it is by searching the inventory information stored in your database for the items in question?automatically. The customer gets the information immediately, without being put on hold listening to annoying canned music or being limited by the hours your service desk is open. And for every customer who uses your Web site, that's one less phone call that needs to be handled by a person on the service desk payroll. (Perhaps the Web site can pay for itself this way?)
But you can put the database to even better use than that. Web-based inventory search requests can provide information not only to your customers but to your company as well. The queries tell you what customers are looking for, and the query results tell you whether or not you're able to satisfy their requests. To the extent that you don't have what they want, you're probably losing business. Consequently, it makes sense to record information about inventory searches?what customers were looking for and whether you had it in stock. Then you can use this information to adjust your inventory and provide better service to your customers.
Another Web-based application for databases is to serve up banner advertisements in Web pages. I don't like them any better than you do, but the fact remains that they are a popular application for MySQL, which can be used to store advertisements and retrieve them for display by a Web server. In addition, MySQL can perform the kind of record keeping often associated with this activity by tracking which ads have been served, how many times they've been displayed, which sites accessed them, and so on.
So how does MySQL work? The best way to find out is to try it for yourself, and for that we'll need a database to work with.