MySQL :: MySQL 8.0 Reference Manual :: B.3.3.2 How to Reset the Root Password

If you have never assigned a root password for MySQL, the server does not require a password at all for connecting as root. However, this is insecure. For instructions on assigning a password, see Section 2.9.4, “Securing the Initial MySQL Account”. If you know the root password and want to change it, see Section 15.7.1.1, “ALTER USER Statement”, and Section 15.7.1.10, “SET PASSWORD Statement”. If

[piglovesyou]

MySQL 5.5 でrootユーザのパスワードを忘れたりしてログインできなくなったらやること