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Logging On to MySQL

The standard interface for working with MySQL databases is to connect to the

MySQL server software (which you set up in Chapter 1) and type commands

one at a time. To make this connection to the server, you'll need the MySQL

client program. If you installed the MySQL server software yourself, either under

Windows or under some brand of UNIX, you already have this program installed

in the same location as the server program. Under Linux, for example, the program

is called mysql and is located by default in the /usr/local/mysql/bin directory.

Under Windows, the program is called mysql.exe and is located by default in

the C:\mysql\bin directory.

If you didn't set up the MySQL server yourself (if, for example, you'll be working

on your Web host's MySQL server), there are two ways to connect to the MySQL

server. The first is to use Telnet or a Secure Shell (SSH) connection to log into

your Web host's server, and then run mysql from there. The second is to download

and install the MySQL client software from http://www.mysql.com/ (available

free for Windows and Linux) on your own computer, and use it to connect to

the MySQL server over the Internet. Both methods work well, and your Web

host may support one, the other, or both — you'll need to ask.

Warning

Many Web hosts do not allow direct access to their MySQL servers over

the Internet for security reasons. If your host has adopted this policy

(you'll have to ask them if you're not sure), installing the MySQL client

software on your own computer won't do you any good. Instead, you'll

need to install a Web-based MySQL administration script onto your site.

phpMyAdminii is the most popular one available; indeed, many Web

hosts will configure your account with a copy of phpMyAdmin for you.

While Web-based MySQL administration systems provide a convenient,

graphical interface for working with your MySQL databases, it is still

important to learn the basics of MySQL's command-line interface. The

commands you use in this interface are the very same commands you'll

have to include in your PHP code later in this book. I therefore recommend

going back to Chapter 1 and installing MySQL on your own computer

so you can complete the exercises in this chapter before getting

comfortable with your Web-based administration interface.

iihttp://www.phpmyadmin.net/

37

Logging On to MySQL

Whichever method and operating system you use, you'll end up at a command

line, ready to run the MySQL client program and connect to your MySQL server.

Here's what you should type:

mysql -h hostname –u username -p

You need to replace hostname with the host name or IP address of the computer

on which the MySQL server is running. If the client program is run on the same

computer as the server, you can actually leave off the -h hostname part of the

command instead of typing -h localhost or –h 127.0.0.1. username should be

your MySQL user name. If you installed the MySQL server yourself, this will

just be root. If you're using your Web host's MySQL server, this should be the

MySQL user name they assigned you.

The -p argument tells the program to prompt you for your password, which it

should do as soon as you enter the command above. If you set up the MySQL

server yourself, this password is the root password you chose in Chapter 1. If

you're using your Web host's MySQL server, this should be the MySQL password

they gave you.

If you typed everything properly, the MySQL client program will introduce itself

and then dump you on the MySQL command line:

mysql>

Now, the MySQL server can actually keep track of more than one database. This

allows a Web host to set up a single MySQL server for use by several of its subscribers

, for example. So your next step should be to choose a database with

which to work. First, let's retrieve a list of databases on the current server. Type

this command (don't forget the semicolon!), and press Enter.

mysql>SHOW DATABASES;

MySQL will show you a list of the databases on the server. If this is a brand new

server (i.e. if you installed this server yourself in Chapter 1), the list should look

like this:

+----------+

| Database |

+----------+

| mysql |

| test |

+----------+

2 rows in set (0.11 sec)

38

Getting Started with MySQL

The MySQL server uses the first database, called mysql, to keep track of users,

their passwords, and what they're allowed to do. We'll steer clear of this database

for the time being, and come back to it in Chapter 8 when we discuss MySQL

Administration. The second database, called test, is a sample database. You can

actually get rid of this database. I won't be referring to it in this book, and we'll

create our own example database momentarily. Deleting something in MySQL

is called "dropping" it, and the command for doing so is appropriately named:

mysql>DROP DATABASE test;

If you type this command and press Enter, MySQL will obediently delete the

database, saying "Query OK" in confirmation. Notice that you're not prompted

with any kind of "are you sure?" message. You have to be very careful to type

your commands correctly in MySQL because, as this example shows, you can

obliterate your entire database—along with all the information it contains—with

one single command!

Before we go any further, let's learn a couple of things about the MySQL command

line. As you may have noticed, all commands in MySQL are terminated by a

semicolon (;). If you forget the semicolon, MySQL will think you haven't finished

typing your command, and will let you continue to type on another line:

mysql>SHOW

->DATABASES;

MySQL shows you that it's waiting for you to type more of your command by

changing the prompt from mysql> to ->. For long commands, this can be handy,

as it allows you to spread your commands out over several lines.

If you get halfway through a command and realize you made a mistake early on,

you may want to cancel the current command entirely and start over from scratch.

To do this, type \c and press Enter:

mysql>DROP DATABASE\c

mysql>

MySQL will completely ignore the command you had begun to type, and will go

back to the prompt to wait for another command.

Finally, if at any time you want to exit the MySQL client program, just type quit

or exit (either one will work). This is the only command that doesn't need a

semicolon, but you can use one if you want to.

39

Logging On to MySQL

mysql>quit

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