PowerCMS Xで複数のモデルのデータを日付順に並べる

(SELECT 'blog' as model, `blog_id` as id, `blog_published_on` as published_on FROM `mt_blog`)
UNION
(SELECT 'event' as model, `event_id` as id, `event_published_on` as published_on FROM `mt_event`)
UNION
(SELECT 'report' as model, `report_id` as id, `report_published_on` as published_on FROM `mt_report`)
UNION
(SELECT 'recruitment' as model, `recruitment_id` as id, `recruitment_published_on` as published_on FROM `mt_recruitment`)
ORDER BY published_on DESC LIMIT 20;