Database error (# Error establishing a database connection.)

when I filled all data in then run but I get this type of error.

Error establishing a database connection.

please suggest asap.
This either means that the username and password information in your wp-config.php file is incorrect or we can’t contact the database server at localhost. This could mean your host’s database server is down.

  • Are you sure you have the correct username and password?
  • Are you sure you have typed the correct hostname?
  • Are you sure the database server is running?