We set up child collection relationship to Fetch as Join in mapping, using fluentNHibernate:
HasMany( x => Details ).Fetch.Join();
It works fine at least for Session.Get<T>(id), we can see only one joined query instead of two separated ones.
But it seems Session.Query<T>() keeps ignoring this join fetch setting, we always got two separated selects when using Session.Query<T>. A Bug?