How to resolve the MySQL database connection failure问题

There are several possible reasons for MySQL database connection failure, below are several possible solutions:

1. Check if the MySQL service has been started: Check in the command line or service center to see if the MySQL service has been started. If not, you can try starting it manually.
2. Check the MySQL configuration file: Open the MySQL configuration file (usually my.cnf or my.ini) and make sure the database connection parameters such as host name, port number, username, and password are correct.
3. Check the network connection: Ensure that the network connection is working properly by trying the ping command or telnet command to check if the host and port are reachable.
4. Check firewall settings: If a firewall is being used, make sure that the MySQL port is open. You can either try disabling the firewall or configuring firewall rules to allow access to the MySQL port.
5. Check database permissions: Make sure that the user connecting to MySQL has sufficient permissions. You can try connecting with the root user – if successful, it indicates a permissions issue. Consider granting additional permissions to other users.
6. Check MySQL logs: Viewing MySQL error logs can provide useful information such as specific connection error messages or reasons for connection failures.
7. Check the compatibility of MySQL version: If using a newer version of MySQL client to connect to an older version of MySQL server, there may be compatibility issues. You can try upgrading or downgrading either the MySQL client or server version.

If none of the above methods solve the issue, it may be necessary to further investigate the problem by referring to relevant technical documents or seeking help from the MySQL community.