一般是使用flush privileges; 讓權限生效.
https://dev.mysql.com/doc/refman/5.7/en/privilege-changes.html
裡面有提到
If you modify the grant tables directly using statements such as INSERT, UPDATE, or DELETE (which is not recommended), the changes have no effect on privilege checking until you either tell the server to reload the tables or restart it. Thus, if you change the grant tables directly but forget to reload them, the changes have no effect until you restart the server. This may leave you wondering why your changes seem to make no difference!