So, I have a Model `House`, and a house can `have_many` `Room`s.

I would like to delete all records of `House` that have no `Room`s.

I've tried 

```
House.includes(:room).having('room.id IS NULL')

```

which errors, as does 

```
House.all().where(:room.count == 0)

```

and many other things that I've tried along the same lines.

I'm probably missing something really straightforward, anyone have any ideas?