I'm not sure this will ever be possible considering even switching to different RDBMS that do have a standard (SQL) is usually non trivial. BTW when people say

I'm not sure this will ever be possible considering even switching to different RDBMS that do have a standard (SQL) is usually non trivial. BTW when people say cloud here I assume they mean PaaS and not IaaS because IaaS has many standards (openstack).