tructure of a typical database table

An Introduction to Databases

As I've already explained, PHP is a server-side scripting language that lets you

insert into your Web pages instructions that your Web server software (be it

Apache, IIS, or whatever) will execute before it sends those pages to browsers

that request them. In a brief example, I showed how it was possible to insert the

current date into a Web page every time it was requested.

Now that's all well and good, but things really get interesting when a database is

added to the mix. 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 scripting 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 Website.

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

file for each of your jokes, you could write a single PHP file that was designed to

fetch any joke out of the database and display it. Second, adding a joke to your

Website 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.

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

things. For our joke database, we'd probably start with a table called Jokes 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 Jokes table might have columns for the text of the

jokes, and the dates on which the jokes were added to the database. Each joke

that we stored in this table would then be said to be a row in the table. These

rows and columns form a table that looks like Figure 2.1.

Figure 2.1. Structure of a typical database table

Notice that, in addition to columns for the joke text (JokeText) and the date of

the joke (JokeDate), I included a column named ID. As a matter of good design,

a database table should always provide a way to identify uniquely each of its

rows. 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 we have an easy way to refer to them, and to keep track

of which joke is which. Such database design issues will be covered in greater

depth in Chapter 5.

So, to review, the above 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 our belts,

we're ready to get started with MySQL.

Getting Started with MySQL