У вас есть календарь, круто.Просто используйте его слева от ЛЕВОГО СОЕДИНЕНИЯ:
SELECT Calendar.Date, YourData.*
FROM Calendar
LEFT JOIN YourData ON Calendar.Date BETWEEN startDate AND endDate
WHERE Calendar.Date BETWEEN '2018-11-01' AND '2018-11-30'
Если вы хотите все пары дата-продукт, то добавьте CROSS JOIN:
SELECT Calendar.Date, Products.Product, YourData.*
FROM Calendar
CROSS JOIN (
SELECT Product
FROM YourData
GROUP BY Product
) AS Products
LEFT JOIN YourData ON
Calendar.Date BETWEEN startDate AND endDate AND
Products.Product = YourData.Product
WHERE Calendar.Date BETWEEN '2018-11-01' AND '2018-11-30'