SELECT
  d.id AS d_id,
  CONCAT_WS(" ",d.first_name,d.last_name) AS driver,
  SUM(dh.time_diff)  AS d_hours
FROM
  drivers AS d LEFT JOIN driver_hours AS dh ON (dh.driver_id=d.id)
WHERE
 dh.start_time BETWEEN '2004-01-21 00:00:00' AND '2005-01-26 00:00:00'
GROUP BY
  d.id
ORDER BY
 d.signal_no+ 0 

SELECT
  d.id AS d_id,
  CONCAT_WS(" ",d.first_name,d.last_name) AS driver,
  COUNT(o.id) AS o_count
FROM
  drivers AS d LEFT JOIN orders AS o ON (o.driver_id=d.id)
WHERE
  o.post_date  BETWEEN '2004-01-21 00:00:00' AND '2005-01-27 00:00:00'
GROUP BY
  d.id
ORDER BY
 d.signal_no+ 0