mysql - Displaying zero valued months with SQL

Question

The following query returns values for months with sales but not for months where sales are zero:

SELECT DATE_FORMAT(O.OrderDate, "%b, %Y") AS MonthYear, SUM(O.Total * C.Rate) AS Sales 
FROM (Orders O INNER JOIN OrdersStates OS ON O.OrderID = OS.OrderID)
INNER JOIN Users U ON U.UserID = O.UserID
INNER JOIN UsersDescription UD ON U.UserID = UD.UserID
INNER JOIN States S ON S.StateID = OS.StateID INNER JOIN Currencies C ON O.Currency = C.Abb 
WHERE O.OrderDate >= '2009-10-01 00:00:00' AND O.OrderDate < '2010-04-19 23:59:59' 
GROUP BY MonthYear ORDER BY MonthYear

The goal is to make it return a zero value in months where there are no sales. Can anyone see what is missing?

Thank you in advance,

Orville

Answer 1

While not impossible, it's not easy to do this in SQL.

Since it is mostly a presentation issue it would probably be easier to add the missing rows in the client after you have executed the query in your question by iterating over the results and checking for missing months.