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An Introduction to Databases By: Kevin Yank June 15th, 2010 Reader Rating: 9

About the Author

A database server (in our case, MySQL) is a program that can store large amounts of information in an organized format that’s easily accessible through programming languages like PHP. For example, you could tell PHP to look in the database for a list of jokes that you’d like to appear on your web site.

Kevin Yank

In this example, the jokes would be stored entirely in the database. The advantages of this approach would be twofold: First, instead of having to write an HTML page for each of your jokes, you could write a single PHP script that was designed to fetch any joke from the database and display it by generating an HTML page for it on the fly. Second, adding a joke to your web site would be a simple matter of inserting the joke into the database. The PHP code would take care of the rest, automatically displaying the new joke along with the others when it fetched the list from the database.

Kevin began developing for the Web in 1995 and is a highly respected technical author. He wrote Build your own Database Driven Website using PHP and MySQL, a practical step-by-step guide published by SitePoint, and he's co-author of the SitePoint Tech Times, a bi-weekly newsletter for technically-minded web developers. Kev believes that any good webmaster should have seen at least one episode of MacGyver.

View all articles by Kevin Y ank... Let’s run with this example as we look at how data is stored in a database. A database is composed of one or more tables, each of which contains a list of items, or things. For our joke database, we’d probably start with a table called joke that would contain a list of jokes. Each table in a database has one or more columns, or fields. Each column holds a certain piece of information about each item in the table. In our example, our joke table might have one column for the text of the jokes, and another for the dates on which the jokes were added to the database. Each joke stored in this way would then be said to be a row or entry in the table. These rows and columns form a table that looks like Figure 1, “A typical database table containing a list of jokes”.

Figure 1. A typical database table containing a list of jokes

Notice that, in addition to columns for the joke text (joketext) and the date of the joke (jokedate), I’ve included a column named id. As a matter of good design, a database table should always provide a means by which we can identify each of its rows uniquely. Since it’s possible that a single joke could be entered more than once on the same date, the joketext and jokedate columns can’t be relied upon to tell all the jokes apart. The function of the id column, therefore, is to assign a unique number to each joke so that we have an easy way to refer to them and to keep track of which joke is which. We’ll take a closer look at database design issues like this next week. So, to review, the table in Figure 1, “A typical database table containing a list of jokes” is a three-column table with two rows, or entries. Each row in the table contains three fields, one for each column in the table: the joke’s ID, its text, and the date of the joke. With this basic terminology under your belt, you’re ready to dive into using MySQL.

14/12/2010 14:38

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