Grant access on a database to all users I have a global database, as I all users should have access to it. Is it possible to grant permission on a database to all users? something like

GRANT ALL ON my_database.* TO *@localhost;


Even (for security reason), it can be read permission only.
Yes, this is possible, though not recommended. You can create a user with an empty string as username, also known as the anonymous user. It matches any username. This is the only possibility, wildcards like in the hostname (i.e. 'user'@'%.any.domain.de') are not allowed.

GRANT ALL ON my_database.* TO ''@'localhost';