create database mysqltest1;
create database mysqltest2;
create user foo@localhost;
create role r1, r2;
grant all on mysqltest1.* to r1;
grant all on mysqltest2.* to r2;
grant r1 to r2;
grant r2 to foo@localhost;
connect  foo,localhost,foo,,;
select current_user;
current_user
foo@localhost
show tables in mysqltest1;
ERROR 42000: Access denied for user 'foo'@'localhost' to database 'mysqltest1'
show tables in mysqltest2;
ERROR 42000: Access denied for user 'foo'@'localhost' to database 'mysqltest2'
set role r2;
show tables in mysqltest1;
Tables_in_mysqltest1
show tables in mysqltest2;
Tables_in_mysqltest2
show grants;
Grants for foo@localhost
GRANT `r2` TO `foo`@`localhost`
GRANT USAGE ON *.* TO `foo`@`localhost`
GRANT `r1` TO `r2`
GRANT USAGE ON *.* TO `r2`
GRANT ALL PRIVILEGES ON `mysqltest2`.* TO `r2`
GRANT USAGE ON *.* TO `r1`
GRANT ALL PRIVILEGES ON `mysqltest1`.* TO `r1`
connection default;
drop user foo@localhost;
drop role r1;
drop role r2;
drop database mysqltest1;
drop database mysqltest2;