JavaScript Editor Source code editor     What Is Ajax 

Main Page

Chapter 3. Tutorial

Table of Contents

3.1. Connecting to and Disconnecting from the Server
3.2. Entering Queries
3.3. Creating and Using a Database
3.3.1. Creating and Selecting a Database
3.3.2. Creating a Table
3.3.3. Loading Data into a Table
3.3.4. Retrieving Information from a Table
3.4. Getting Information About Databases and Tables
3.5. Using mysql in Batch Mode
3.6. Examples of Common Queries
3.6.1. The Maximum Value for a Column
3.6.2. The Row Holding the Maximum of a Certain Column
3.6.3. Maximum of Column per Group
3.6.4. The Rows Holding the Group-wise Maximum of a Certain Field
3.6.5. Using User-Defined Variables
3.6.6. Using Foreign Keys
3.6.7. Searching on Two Keys
3.6.8. Calculating Visits Per Day
3.7. Queries from the Twin Project
3.7.1. Find All Non-distributed Twins
3.7.2. Show a Table of Twin Pair Status
3.8. Using MySQL with Apache

This chapter provides a tutorial introduction to MySQL by showing how to use the mysql client program to create and use a simple database. mysql (sometimes referred to as the “terminal monitor” or just “monitor”) is an interactive program that allows you to connect to a MySQL server, run queries, and view the results. mysql may also be used in batch mode: you place your queries in a file beforehand, then tell mysql to execute the contents of the file. Both ways of using mysql are covered here.

To see a list of options provided by mysql, invoke it with the --help option:

shell> mysql --help

This chapter assumes that mysql is installed on your machine and that a MySQL server is available to which you can connect. If this is not true, contact your MySQL administrator. (If you are the administrator, you need to consult the relevant portions of this manual, such as Chapter 5, Database Administration.)

This chapter describes the entire process of setting up and using a database. If you are interested only in accessing an existing database, you may want to skip over the sections that describe how to create the database and the tables it contains.

Because this chapter is tutorial in nature, many details are necessarily omitted. Consult the relevant sections of the manual for more information on the topics covered here.

3.1. Connecting to and Disconnecting from the Server

To connect to the server, you will usually need to provide a MySQL user name when you invoke mysql and, most likely, a password. If the server runs on a machine other than the one where you log in, you will also need to specify a host name. Contact your administrator to find out what connection parameters you should use to connect (that is, what host, user name, and password to use). Once you know the proper parameters, you should be able to connect like this:

shell> mysql -h host -u user -p
Enter password: ********

host and user represent the host name where your MySQL server is running and the user name of your MySQL account. Substitute appropriate values for your setup. The ******** represents your password; enter it when mysql displays the Enter password: prompt.

If that works, you should see some introductory information followed by a mysql> prompt:

shell> mysql -h host -u user -p
Enter password: ********
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 25338 to server version: 5.0.46-standard

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.


The mysql> prompt tells you that mysql is ready for you to enter commands.

If you are logging in on the same machine that MySQL is running on, you can omit the host, and simply use the following:

shell> mysql -u user -p

If, when you attempt to log in, you get an error message such as ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2), it means that that MySQL server daemon (Unix) or service (Windows) is not running. Consult the administrator or see the section of Chapter 2, Installing and Upgrading MySQL that is appropriate to your operating system.

For help with other problems often encountered when trying to log in, see Section B.1.2, “Common Errors When Using MySQL Programs”.

Some MySQL installations allow users to connect as the anonymous (unnamed) user to the server running on the local host. If this is the case on your machine, you should be able to connect to that server by invoking mysql without any options:

shell> mysql

After you have connected successfully, you can disconnect any time by typing QUIT (or \q) at the mysql> prompt:

mysql> QUIT

On Unix, you can also disconnect by pressing Control-D.

Most examples in the following sections assume that you are connected to the server. They indicate this by the mysql> prompt.


JavaScript Editor Source code editor     What Is Ajax