SQL query to compare product sales by month

Question

I have a Monthly Status database view I need to build a report based on. The data in the view looks something like this:

Category | Revenue  |  Yearh  |  Month
B         


        

Answer 1

The trick is to do a FULL JOIN, with ISNULL's to get the joined columns from either table. I usually wrap this into a view or derived table, otherwise you need to use ISNULL in the WHERE clause as well.

SELECT 
    Program,
    Month,
    ThisYearTotalRevenue,
    PriorYearTotalRevenue
FROM (
    SELECT 
        ISNULL(ThisYear.Program, PriorYear.Program) as Program,
        ISNULL(ThisYear.Month, PriorYear.Month),
        ISNULL(ThisYear.TotalRevenue, 0) as ThisYearTotalRevenue,
        ISNULL(PriorYear.TotalRevenue, 0) as PriorYearTotalRevenue
    FROM (
        SELECT Program, Month, SUM(TotalRevenue) as TotalRevenue 
        FROM PVMonthlyStatusReport 
        WHERE Year = @FinancialYear 
        GROUP BY Program, Month
    ) as ThisYear 
    FULL OUTER JOIN (
        SELECT Program, Month, SUM(TotalRevenue) as TotalRevenue 
        FROM PVMonthlyStatusReport 
        WHERE Year = (@FinancialYear - 1) 
        GROUP BY Program, Month
    ) as PriorYear ON
        ThisYear.Program = PriorYear.Program
        AND ThisYear.Month = PriorYear.Month
) as Revenue
WHERE 
    Program = 'Bikes'
ORDER BY 
    Month

That should get you your minimum requirements - rows with sales in either 2007 or 2008, or both. To get rows with no sales in either year, you just need to INNER JOIN to a 1-12 numbers table (you do have one of those, don't you?).