create user 'test_user'@'localhost';
create user 'test_role1'@'';
create user 'test_role2'@'';
update mysql.user set is_role='Y' where user='test_role1';
update mysql.user set is_role='Y' where user='test_role2';
insert into mysql.roles_mapping (HostFk, UserFk, RoleFk) values ('localhost',
'test_user',
'test_role1');
insert into mysql.roles_mapping (HostFk, UserFk, RoleFk) values ('localhost',
'test_user',
'test_role2');
insert into mysql.roles_mapping (HostFk, UserFk, RoleFk) values ('',
'test_role1',
'test_role2');
select user, host from mysql.user where user not like 'root';
user	host
test_role1	
test_role2	
test_user	localhost
select * from mysql.roles_mapping;
HostFk	UserFk	RoleFk
	test_role1	test_role2
localhost	test_user	test_role1
localhost	test_user	test_role2
flush privileges;
select user, host from mysql.db;
user	host
	%
	%
grant select on mysql.* to test_role2@'';
flush privileges;
select * from mysql.roles_mapping;
ERROR 42000: SELECT command denied to user 'test_user'@'localhost' for table 'roles_mapping'
select current_user(), current_role();
current_user()	current_role()
test_user@localhost	NONE
set role test_role1;
select current_user(), current_role();
current_user()	current_role()
test_user@localhost	test_role1
select * from mysql.roles_mapping;
HostFk	UserFk	RoleFk
	test_role1	test_role2
localhost	test_user	test_role1
localhost	test_user	test_role2
set role none;
select current_user(), current_role();
current_user()	current_role()
test_user@localhost	NONE
select * from mysql.roles_mapping;
ERROR 42000: SELECT command denied to user 'test_user'@'localhost' for table 'roles_mapping'
set role test_role2;
select current_user(), current_role();
current_user()	current_role()
test_user@localhost	test_role2
select * from mysql.roles_mapping;
HostFk	UserFk	RoleFk
	test_role1	test_role2
localhost	test_user	test_role1
localhost	test_user	test_role2
drop user 'test_user'@'localhost';
revoke select on mysql.* from test_role2@'';
delete from mysql.user where user='test_role1';
delete from mysql.user where user='test_role2';
delete from mysql.roles_mapping where RoleFk='test_role1';
delete from mysql.roles_mapping where RoleFk='test_role2';
flush privileges;