
UPDATE wap_r_resource as r1,
(
  SELECT r.resource_id, v.wistia_thumbnail
  FROM wap_r_resource r
  JOIN was_wistia_video v ON v.wistia_video_id = r.wistia_video_id
  WHERE r.type_id = 5
  AND r.video_start_image = ''
) as r2
SET r1.video_start_image = r2.wistia_thumbnail
WHERE r1.resource_id = r2.resource_id;
