MySQL

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Chapter 1: Introduction to MySQL and SQL

Begin here if you are new to databases and perhaps uncertain whether or not you need one or can use one.You should also read the chapter if you don't know anything about MySQL or SQL and need an introductory guide to get started. Readers who have experience with MySQL or with database systems might want to skim through the material. However, everybody should read the section "A Sample Database" because it's best if you're familiar with the purpose and contents of the database that we'll be using repeatedly throughout the book.

How MySQL Can Help You

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 "A Sample Database."

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 use its notepad function for a grocery list, not its database capabilities.

The power of a database system comes in when the information you want to organize and manage becomes voluminous or complex so that your records become more burdensome than you care to deal with by hand. Databases can be used by large corporations processing millions of transactions a day, of course. 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 situations 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 who 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 inventory 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 at which 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 place you've been would help you avoid repeats.You'd also like to note how wen your talks are received. (Your address "Why I Love Cats" to 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 large amounts to relatively small 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 seen in the...

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