create user test_user@localhost;
create role test_role1;
grant test_role1 to test_user@localhost;
select user, host from mysql.user where user not like 'root';
user	host
test_role1	
test_user	localhost
select * from mysql.roles_mapping;
Host	User	Role	Admin_option
localhost	root	test_role1	Y
localhost	test_user	test_role1	N
grant select on *.* to test_role1;
select * from mysql.user where user='test_role1';
Host	User	Password	Select_priv	Insert_priv	Update_priv	Delete_priv	Create_priv	Drop_priv	Reload_priv	Shutdown_priv	Process_priv	File_priv	Grant_priv	References_priv	Index_priv	Alter_priv	Show_db_priv	Super_priv	Create_tmp_table_priv	Lock_tables_priv	Execute_priv	Repl_slave_priv	Repl_client_priv	Create_view_priv	Show_view_priv	Create_routine_priv	Alter_routine_priv	Create_user_priv	Event_priv	Trigger_priv	Create_tablespace_priv	ssl_type	ssl_cipher	x509_issuer	x509_subject	max_questions	max_updates	max_connections	max_user_connections	plugin	authentication_string	password_expired	is_role
	test_role1		Y	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N					0	0	0	0			N	Y
select * from mysql.roles_mapping;
ERROR 42000: SELECT command denied to user 'test_user'@'localhost' for table 'roles_mapping'
show grants;
Grants for test_user@localhost
GRANT USAGE ON *.* TO 'test_user'@'localhost'
GRANT test_role1 TO 'test_user'@'localhost'
select current_user(), current_role();
current_user()	current_role()
test_user@localhost	NULL
set role test_role1;
select current_user(), current_role();
current_user()	current_role()
test_user@localhost	test_role1
show grants;
Grants for test_user@localhost
GRANT SELECT ON *.* TO 'test_role1'
GRANT USAGE ON *.* TO 'test_user'@'localhost'
GRANT test_role1 TO 'test_user'@'localhost'
select * from mysql.roles_mapping;
Host	User	Role	Admin_option
localhost	root	test_role1	Y
localhost	test_user	test_role1	N
set role none;
select current_user(), current_role();
current_user()	current_role()
test_user@localhost	NULL
select * from mysql.roles_mapping;
ERROR 42000: SELECT command denied to user 'test_user'@'localhost' for table 'roles_mapping'
delete from mysql.user where user='test_role1';
delete from mysql.roles_mapping where Role='test_role1';
flush privileges;
drop user 'test_user'@'localhost';
