Mysql - group by всегда отображает столбец первой строки?

Сначала создайте таблицу календаря

SELECT coalesce(COUNT(O.*),0) as Norders, DATE_FORMAT(C.date, "%M %e") as sdate 
FROM Calendar C 
  LEFT JOIN ORDERS O ON C.date=O.date
WHERE O.date <= NOW() AND O.date >= NOW() - INTERVAL 1 MONTH 
GROUP BY DAY(date) 
ORDER BY date ASC;