SELECT t1.id
FROM HEAPM_Job AS t1, (
    SELECT MIN(job.id) AS id
    FROM HEAPM_Job AS job
    LEFT JOIN HEAPM_Job AS parent_tbl ON parent_tbl.id = job.parent
    WHERE
      (parent_tbl.status = 'completed' OR parent_tbl.status IS NULL)
    AND
      job.status = 'queued'
    GROUP BY job.related
  ) AS t2
WHERE
  t1.id=t2.id
ORDER BY t1.priority DESC