ERROR 1045 (28000): Access denied for user ''@'%' (using password: YES) code example

Example 1: windows error 1045 (28000): access denied for user 'root'@'localhost' (using password: yes)

update user set authentication_string=password('my_password') where user='root';

Example 2: ERROR 1045 (28000): Access denied for user 'ananyapam'@'localhost' (using password: NO)

sudo mysql -u root -p