SELECT e.* FROM mdl_event e
INNER JOIN (
  SELECT ev.modulename, ev.instance, ev.eventtype, MIN(ev.priority) as priority FROM (
    SELECT modulename, instance, eventtype, priority FROM mdl_event ev
      WHERE (ev.userid = ? AND ev.courseid = ? AND ev.groupid = ? AND ev.categoryid = ?) UNION
        SELECT modulename, instance, eventtype, priority FROM mdl_event ev
          WHERE (ev.groupid != ? AND ev.eventtype = ?) UNION
          SELECT modulename, instance, eventtype, priority FROM mdl_event ev
            WHERE (ev.groupid = ? AND ev.courseid IN (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?) AND ev.categoryid = ?) UNION
            SELECT modulename, instance, eventtype, priority FROM mdl_event ev
              WHERE (ev.categoryid != ? AND ev.eventtype = ?)) ev
              GROUP BY ev.modulename, ev.instance, ev.eventtype
) fe ON e.modulename = fe.modulename AND e.instance = fe.instance AND e.eventtype = fe.eventtype AND (e.priority = fe.priority OR (e.priority IS NULL AND fe.priority IS NULL))
LEFT JOIN mdl_modules m ON e.modulename = m.name
  WHERE (m.visible = ? OR m.visible IS NULL) AND type = ? AND timesort >= ? AND timesort <= ? AND ((e.userid = ? AND e.courseid = ? AND e.groupid = ? AND e.categoryid = ?) OR e.groupid != ? OR (e.groupid = ? AND e.courseid IN (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)) OR (e.groupid = ? AND e.courseid = ? AND e.categoryid != ?)) AND (e.visible = ?)
  ORDER BY COALESCE(e.timesort, e.timestart) ASC, e.id ASC LIMIT ?, ?