4.2.2 Connecting to the MySQL Server

For a client program to be able to connect to the MySQL server, it must use the proper connection parameters, such as the name of the host where the server is running and the user name and password of your MySQL account. Each connection parameter has a default value, but you can override them as necessary using program options specified either on the command line or in an option file.

The examples here use the mysql client program, but the principles apply to other clients such as mysqldump, mysqladmin, or mysqlshow.

This command invokes mysql without specifying any connection parameters explicitly:

shell> mysql

Because there are no parameter options, the default values apply:

To specify the host name and user name explicitly, as well as a password, supply appropriate options on the command line:

shell> mysql --host=localhost --user=myname --password=mypass mydb
shell> mysql -h localhost -u myname -pmypass mydb

For password options, the password value is optional:

As just mentioned, including the password value on the command line can be a security risk. To avoid this problem, specify the --password or -p option without any following password value:

shell> mysql --host=localhost --user=myname --password mydb
shell> mysql -h localhost -u myname -p mydb

When the password option has no password value, the client program prints a prompt and waits for you to enter the password. (In these examples, mydb is not interpreted as a password because it is separated from the preceding password option by a space.)

On some systems, the library routine that MySQL uses to prompt for a password automatically limits the password to eight characters. That is a problem with the system library, not with MySQL. Internally, MySQL does not have any limit for the length of the password. To work around the problem, change your MySQL password to a value that is eight or fewer characters long, or put your password in an option file.

On Unix, MySQL programs treat the host name localhost specially, in a way that is likely different from what you expect compared to other network-based programs. For connections to localhost, MySQL programs attempt to connect to the local server by using a Unix socket file. This occurs even if a --port or -P option is given to specify a port number. To ensure that the client makes a TCP/IP connection to the local server, use --host or -h to specify a host name value of 127.0.0.1, or the IP address or name of the local server. You can also specify the connection protocol explicitly, even for localhost, by using the --protocol=TCP option. For example:

shell> mysql --host=127.0.0.1
shell> mysql --protocol=TCP

The --protocol option enables you to establish a particular type of connection even when the other options would normally default to some other protocol.

On Windows, you can force a MySQL client to use a named-pipe connection by specifying the --pipe or --protocol=PIPE option, or by specifying . (period) as the host name. If named-pipe connections are not enabled, an error occurs. Use the --socket option to specify the name of the pipe if you do not want to use the default pipe name.

Connections to remote servers always use TCP/IP. This command connects to the server running on remote.example.com using the default port number (3306):

shell> mysql --host=remote.example.com

To specify a port number explicitly, use the --port or -P option:

shell> mysql --host=remote.example.com --port=13306

You can specify a port number for connections to a local server, too. However, as indicated previously, connections to localhost on Unix will use a socket file by default. You will need to force a TCP/IP connection as already described or any option that specifies a port number will be ignored.

For this command, the program uses a socket file on Unix and the --port option is ignored:

shell> mysql --port=13306 --host=localhost

To cause the port number to be used, invoke the program in either of these ways:

shell> mysql --port=13306 --host=127.0.0.1
shell> mysql --port=13306 --protocol=TCP

The following list summarizes the options that can be used to control how client programs connect to the server:

It is possible to specify different default values to be used when you make a connection so that you need not enter them on the command line each time you invoke a client program. This can be done in a couple of ways: