What are the reasons why the MySQL database cannot connect?

There could be several reasons why the MySQL database connection is not working.

1. Server not running: check if the MySQL server has been started.
2. The server isn’t running on the port: By default, the MySQL server runs on port 3306, make sure to use the correct port when connecting.
3. Firewall blocking connection: The firewall may block connections to port 3306, check firewall settings and ensure that connections to the MySQL server are allowed.
4. The username or password is incorrect: please check if the username and password in the login information are correct.
5. Insufficient database permissions: Ensure that the user connecting has the correct permissions to access the database.
6. Incorrect database name: make sure the correct database name is specified when connecting.
7. Internet issue: Check if the network connection is working properly, try using a different network connection to see if the problem can be resolved.
8. Configuration issue with MySQL server: Check if the configuration file of MySQL server has correctly set network access permissions.
9. Ensure the MySQL client and server are compatible versions to avoid MySQL server compatibility issues.