Error: ER_ACCESS_DENIED_ERROR: Access denied for user 'root'@'localhost' (using password: NO) code example

Example 1: mysql access denied for user 'root'@'localhost'

sudo mysql

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'root';

Example 2: access denied for user 'root'@'localhost' (using password no) stackoverflow

-skip-grant-tables