T-SQL, zero sum for no match for join

Question

I have two tables, one with all my branches and one with all my sales. The sales table also contains the sales representative identifier, branch identifier, month and year.

I need a query that will return the amount of specific rep sales for the year, grouped by branch and month, and the query should return 0 if there were no sales in the branch for that month. I have the following that does not return 0 if there are no sales:

SELECT
    s.Month,
    b.BranchName,
    SUM(s.InvoiceAmount) AS 'Sales'
FROM 
    Branch b
INNER JOIN
    Sales s ON s.BranchID = b.BranchID
WHERE
    s.Year = 2008
AND
    s.SalesRepID= 11
GROUP BY 
    s.Month,
    b.BranchName
ORDER BY 
    s.Month,
    b.BranchName

Answer 1

You will need to add “missing” data to join it.

SELECT
    b.BranchName,
    SUM(ISNULL(s.InvoiceAmount, 0)) AS 'Sales',
    s.Month
FROM 
    Branch b
    LEFT OUTER JOIN (
            SELECT
        b.BranchID AS BranchID
        , s.SalesRepID AS SalesRepID
        , Months.Month AS Month
        , Years.Year AS Year
        , 0 AS InvoiceAmount
      FROM 
          Sales s
          CROSS JOIN (
            SELECT 1 AS Month
            UNION ALL SELECT 2
            UNION ALL SELECT 3
            UNION ALL SELECT 4
            UNION ALL SELECT 5
            UNION ALL SELECT 6
            UNION ALL SELECT 7
            UNION ALL SELECT 8
            UNION ALL SELECT 9
            UNION ALL SELECT 10
            UNION ALL SELECT 11
            UNION ALL SELECT 12
            ) Months
          CROSS JOIN (
            SELECT 2007 AS Year
            UNION ALL SELECT 2008
            UNION ALL SELECT 2009
            ) Years
          CROSS JOIN Branch b
      UNION ALL SELECT 
        s.BranchID AS BranchID
        , s.SalesRepID AS SalesRepID
        , s.Month AS Month
        , s.Year AS Year
        , s.InvoiceAmount AS InvoiceAmount
      FROM Sales s      
    )s ON s.BranchID = b.BranchID    
WHERE
    s.Year = 2008
    AND s.SalesRepID= 11
GROUP BY 
    s.Month,
    b.BranchName
ORDER BY 
    b.BranchName,
    s.Month

Answer 2

LEFT JOIN Sales, , Sales.

Answer 3

NULL, : COALESCE(SUM(...), 0) , NULL, ...

Answer 4

ISNULL .

SELECT

    b.BranchName,
    s.Month,
    SUM(ISNULL(s.InvoiceAmount,0)) AS 'Sales'
FROM 
    Branch b
LEFT JOIN
    Sales s ON s.BranchID = b.BranchID
WHERE
    s.Year = 2008
AND
    s.SalesRepID= 11
GROUP BY 
    s.Month,
    b.BranchName
ORDER BY 
    s.Month,
    b.BranchName

Answer 5

isnull, :

SELECT    b.BranchName
,    SUM(isnull(s.InvoiceAmount, 0)) AS 'Sales'
FROM     Branch b
LEFT JOIN    Sales s ON s.BranchID = b.BranchID 
GROUP BY     s.Month,    b.BranchName
ORDER BY     s.Month,    b.BranchName

, , , .