If you strengthen the root password in MySQL, you will be asked to change the password again.

Thank you for your help.

Please let me know if the database authorization is not successful.

Create a user and database created with the root account.
Grant permission to create a database so that it can be operated by the created user.

Operations

Configured localhost to connect to the database for users logged in as root and already specified.

$mysql>GRANT ALL ON db.*TO'admin'@'localhost';
  ERROR 1819 (HY000): Your password does not satify the current policy requirements

I thought the root password might be low, so I changed it to the following strength (actually another password).
The same error occurs when trying the above again.

GpkdEdTGB@+fTRfQyTWxJ;,hzRmZiPq*WwxVDgxzmt2^DcquHwyE$oxUz#BYvVFA

password validation policy(?)

mysql>SHOW VARIABLES LIKE 'validate_password%';
+--------------------------------------+--------+
| Variable_name | Value |
+--------------------------------------+--------+
| validate_password_check_user_name | OFF|
| validate_password_dictionary_file | |
| validate_password_length | 8 |
| validate_password_mixed_case_count | 1 |
| validate_password_number_count | 1 |
| validate_password_policy | MEDIUM |
| validate_password_special_char_count | 1 |
+--------------------------------------+--------+

As this password is included in the operation, I think the following official requirements have been met.

The MEDIUM policy contains at least one numeric character, one lowercase and one uppercase character, and one special character (non-alphanumeric)
Add a condition that must contain the .

That's all.
It may not matter, but I also reflected the settings, but it didn't change.

mysql>flush privileges;

What's missing?
Or is it possible to solve it by other means?

I apologize for the inconvenience, but please let me know.

Resolved.

GRANT ALL ON db.*TO'admin'@'localhost' identified by'GpkdEdTGB@+fTRfQyTWxJ;,hzRmZiPq*WwxVDgxzmt2^DquHwyE$oxUz#BYvFA';

I thought you were referring to the root side, but there was no password for the user to set it up.