Summarise by week, even for empty rows

Question

I want to summarise the sum of sales.quantity by week, and to show the week number even if there are no sales.

I have setup a weeks table with 1-54 in there to use an ou

Answer 1

Try this:

SELECT Weeks.WeekNum, SUM(sales.quantity) AS sales
FROM Weeks 
LEFT JOIN sales 
       ON Weeks.WeekNum = DATEPART(week, sales.transDate) and
          sales.transDate BETWEEN @fromDate AND @toDate
WHERE Weeks.WeekNum BETWEEN DATEPART(week, @fromDate) AND 
                            DATEPART(week, @toDate)
GROUP BY Weeks.WeekNum