SELECT
   t.milestone AS __group__,
   m.due,
   t.id AS ticket, t.summary, t.component, t.status, 
   t.resolution, t.version, t.type,
   p.value as priority_value, t.priority, t.owner,
   t.changetime AS modified, t.time, t.reporter
  FROM ticket t
  LEFT JOIN enum p ON p.name = t.priority AND p.type = 'priority'
  LEFT JOIN milestone m ON t.milestone = m.name
  ORDER BY (milestone IS NULL), milestone DESC, (status = 'closed'), 
        (CASE status WHEN 'closed' THEN modified ELSE (-1)*p.value END) DESC