It uses subquery when you pass ids in `IN`:

```
DELETE FROM `pose_words` WHERE `pose_words`.`id` IN (SELECT pose_words.id FROM `pose_words` LEFT OUTER JOIN pose_assignments ON pose_assignments.word_id = pose_words.id GROUP BY pose_words.id HAVING COUNT(pose_assignments.id) = 0)
```

where `DELETE FROM  WHERE pose_words.id...` is a query, and this part: 

```
... IN (SELECT pose_words.id FROM `pose_words` LEFT OUTER JOIN pose_assignments ON pose_assignments.word_id = pose_words.id GROUP BY pose_words.id HAVING COUNT(pose_assignments.id) = 0)
```
is subquery.

Just got it after rereading your comment :) See last commit. Fixed.
:+1: