创建新用户时拒绝访问

Question

当我尝试在phpMyAdmin中将用户添加到我的数据库时遇到问题：

ERROR : #1045 - Access denied for user 'root'@'localhost' (using password: YES)

SQL查询如下所示：

CREATE USER 'my_user'@'localhost' IDENTIFIED BY '***';
GRANT ALL PRIVILEGES ON *.* TO 'my_database'@'localhost'
  IDENTIFIED BY '***' WITH
  MAX_QUERIES_PER_HOUR 0
  MAX_CONNECTIONS_PER_HOUR 0
  MAX_UPDATES_PER_HOUR 0
  MAX_USER_CONNECTIONS 0;

我已经以root用户身份登录phpMyAdmin。