I have an SQL query that looks as follows:

```
SELECT 
    a.id user_id, a.type, a.email_address, 
    a.name_first, a.name_last, languages.title as language,
    b.created_at purchased_on, b.expires_at watchable_until,
    c.title,
    d.title topic,
    e.title category,
    f.subject, f.grade
FROM users a,
     user_video_purchases b,
     videos c,
     gradesubject_category_topics d,
     gradesubject_categories e,
     gradesubjects f
JOIN languages ON 
          users.language_preferred_id = languages.id
WHERE a.id = b.user_id
      AND b.video_id = c.id
      AND c.gradesubject_category_topic_id = d.id
      AND d.gradesubject_category_id = e.id
      AND e.gradesubject_id = f.id
ORDER BY purchased_on DESC;

```

This query returns the follow error message:

> 
> Unknown column 'users.language\_preferred\_id' in 'on clause'
> 
> 
> 

The columns exists in the `users` table and as far as I know the `JOIN` is correct. 

Can someone please point out where I might be going wrong?