create user ''@localhost; create user c; grant select on mysql.* to c; create role r1; grant r1 to c; select user(), current_user(); user() current_user() c@localhost @localhost select user from mysql.user group by user; ERROR 42000: SELECT command denied to user ''@'localhost' for table 'user' set role r1; ERROR OP000: Invalid role specification `r1`. drop role r1; drop user c; drop user ''@localhost;