Why Do I Need Both \"%\" and \"localhost\" When Creating MySQL Users?

Understanding Host Specification for MySQL Users: Why Use Both Wildcard and localhost

Creating multiple user accounts with varying host specifications can be confusing, especially when it comes to using wildcard characters ("%") in MySQL. This article aims to clarify the use of "%' and 'localhost' for user creation and explain why both are necessary.

Wildcard Host Specification (%)

The wildcard host character "%" in MySQL user creation grants access to the user from any host. This allows the user to connect to the database from any IP address or network location.

Localhost Host Specification

'localhost' refers to a specific host, namely the local machine where the MySQL server is running. Connections from the local machine are typically made over a UNIX socket or named pipe, providing higher speed and security than TCP/IP connections.

Why Both Host Specifications Are Required

Although using "%" grants access from any host, it does not include 'localhost'. This is because 'localhost' is treated as a unique host by MySQL due to the way it connects to the server. Therefore, explicitly specifying 'localhost' as a host is still necessary for users to connect from the local machine.

Example User Account Creation

To accommodate both remote and local access, one would create four user accounts as follows:

appuser@'%'
appuser@'localhost'
support@'%'
support@'localhost'

• appuser@'%' and support@'%' allow the respective users to connect from any remote host.
• appuser@'localhost' and support@'localhost' enable the users to connect from the local machine (via UNIX socket or named pipe).

Conclusion

Understanding the distinction between "%" and 'localhost' is crucial for effective MySQL user management. Using both specifications ensures that users have access from both remote and local hosts, providing a comprehensive security and access control strategy.

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