MySQL localhost vs. 127.0.0.1: What\'s the Difference in Database Connections?

Mysql localhost != 127.0.0.1

This question explores the distinction between using the host name "localhost" and the IP address "127.0.0.1" when connecting to a MySQL database.

Explanation

In MySQL, the "localhost" hostname maps to a socket, while the IP address "127.0.0.1" refers to a specific network interface. This distinction becomes apparent when granting permissions.

For instance, granting privileges using "localhost" will grant permissions for connections made through the socket, but not through the network interface. Conversely, granting privileges using "127.0.0.1" will grant permissions for connections made through the network interface, but not through the socket.

Granting ALL Privileges on All Databases from All Hosts

To grant root user all privileges on all databases from all hosts, use the following command:

GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION;

This will grant root user access to all databases from any host.

Troubleshooting

If you encounter the error "Unknown database 'created_from_host'" when trying to connect to the database using "localhost," ensure that the following settings are correct:

• Verify that the skip_networking variable is set to OFF.
• Confirm that the root user has the required privileges using the command SHOW GRANTS FOR root.
• Ensure that the root user is listed in the mysql.user table with the appropriate hosts: SELECT user,host FROM mysql.user WHERE user='root';.

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