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SQL Server procedure returning dbNull instead of sum
I have the following stored procedure in SQL Server 2005:
ALTER PROCEDURE dbo.GetBondAmounts
    (
    @Username varchar(20)
    )
AS
    SELECT Bond.ID BondID, Powers.BondAmount + Charges.BondAmount BondAmount,
    BondFee.Amount + Powers.BondPremium + Charges.BondPremium + Forfeiture.CostOfApprehension + Forfeiture.AmountPaid BondTotal,
    BondFee.Amount + Powers.BondPremium + Charges.BondPremium + Forfeiture.CostOfApprehension + Forfeiture.AmountPaid
    - BalanceForgiveness.Amount - Payment.Amount BondBalance
    FROM Bond LEFT OUTER JOIN UserAgency ON Bond.Agency = UserAgency.Agency
    LEFT OUTER JOIN
    (
        SELECT BondID, SUM(AmountForgiven) Amount
        FROM BalanceForgiveness
        GROUP BY BondID
    ) AS BalanceForgiveness ON Bond.ID = BalanceForgiveness.BondID
    LEFT OUTER JOIN
    (
        SELECT Bond, SUM(Amount) Amount
        FROM BondFee
        GROUP BY Bond
    ) AS BondFee ON Bond.ID = BondFee.Bond
    LEFT OUTER JOIN
    (
        SELECT Powers.Bond, SUM(Charge.BondAmount) BondAmount,
        SUM(Charge.BondPremium) BondPremium
        FROM Powers INNER JOIN Charge ON Powers.Surety = Charge.PowerSurety
        AND Powers.PowerPrefix = Charge.PowerPrefix AND Powers.PowerNumber = Charge.PowerNumber
        GROUP BY Bond
    ) AS Powers ON Bond.ID = Powers.Bond
    LEFT OUTER JOIN
    (
        SELECT BondID, SUM(BondAmount) BondAmount, SUM(BondPremium) BondPremium
        FROM ChargeWithoutPower
        GROUP BY BondID
    ) AS Charges ON Bond.ID = Charges.BondID
    LEFT OUTER JOIN
    (
        SELECT Bond, SUM(CostOfApprehension) CostOfApprehension, SUM(AmountPaid) AmountPaid
        FROM Forfeiture
        GROUP BY Bond
    ) AS Forfeiture ON Bond.ID = Forfeiture.Bond
    LEFT OUTER JOIN
    (
        SELECT Bond, SUM(Amount) Amount
        FROM Payment
        GROUP BY Bond
    ) AS Payment ON Bond.ID = Payment.Bond
    WHERE UserAgency.Username = @Username
    OR EXISTS (SELECT * FROM Users WHERE Username = @Username AND Admin = 1)

I am getting a dbNull value for BondAmount, BondTotal, and BondBalance.  Sometimes there will be no Charge rows or no BalanceForgiveness rows, etc.  I think the issue I am getting is that when there is one table that contains no data for the row, that entire calculation becomes null... how do I fix this to give me the correct amount, total, and balance for each and every bond, no matter how many tables have data or don't.

@Albin:  Thank you for your help in getting me to this solution.  Wrapping the SUM in ISNULL actually did nothing, but when I did the following, it worked.  Thanks for helping me get to the solution.
ALTER PROCEDURE dbo.GetBondAmounts
    (
    @Username varchar(20)
    )
AS
    SELECT Bond.ID BondID, (ISNULL(Powers.Amount,0) + ISNULL(Charges.Amount,0)) BondAmount,
    (ISNULL(BondFee.Amount,0) + ISNULL(Powers.Premium,0) + ISNULL(Charges.Premium,0)
    + ISNULL(Forfeiture.CostOfApprehension,0) + ISNULL(Forfeiture.AmountPaid,0) + Bond.StateTax) BondTotal,
    (ISNULL(BondFee.Amount,0) + ISNULL(Powers.Premium,0) + ISNULL(Charges.Premium,0)
    + ISNULL(Forfeiture.CostOfApprehension,0) + ISNULL(Forfeiture.AmountPaid,0) + Bond.StateTax
    - ISNULL(BalanceForgiveness.Amount,0) - ISNULL(Payment.Amount,0)) BondBalance
    FROM Bond LEFT OUTER JOIN UserAgency ON Bond.Agency = UserAgency.Agency
    LEFT OUTER JOIN
    (
        SELECT BondID, SUM(AmountForgiven) Amount
        FROM BalanceForgiveness
        GROUP BY BondID
    ) AS BalanceForgiveness ON Bond.ID = BalanceForgiveness.BondID
    LEFT OUTER JOIN
    (
        SELECT Bond, SUM(Amount) Amount
        FROM BondFee
        GROUP BY Bond
    ) AS BondFee ON Bond.ID = BondFee.Bond
    LEFT OUTER JOIN
    (
        SELECT Powers.Bond, SUM(Charge.BondAmount) Amount,
        ISNULL(SUM(Charge.BondPremium), 0) Premium
        FROM Powers INNER JOIN Charge ON Powers.Surety = Charge.PowerSurety
        AND Powers.PowerPrefix = Charge.PowerPrefix AND Powers.PowerNumber = Charge.PowerNumber
        GROUP BY Bond
    ) AS Powers ON Bond.ID = Powers.Bond
    LEFT OUTER JOIN
    (
        SELECT BondID, SUM(BondAmount) Amount, SUM(BondPremium) Premium
        FROM ChargeWithoutPower
        GROUP BY BondID
    ) AS Charges ON Bond.ID = Charges.BondID
    LEFT OUTER JOIN
    (
        SELECT Bond, SUM(CostOfApprehension) CostOfApprehension, SUM(AmountPaid) AmountPaid
        FROM Forfeiture
        GROUP BY Bond
    ) AS Forfeiture ON Bond.ID = Forfeiture.Bond
    LEFT OUTER JOIN
    (
        SELECT Bond, SUM(Amount) Amount
        FROM Payment
        GROUP BY Bond
    ) AS Payment ON Bond.ID = Payment.Bond
    WHERE UserAgency.Username = @Username
    OR EXISTS (SELECT * FROM Users WHERE Username = @Username AND Admin = 1)


Wrap your sums in ISNULL.
ISNULL (SUM(Charge.BondAmount), 0)

If you want the sum to be 0 when there are no elements to sum.

I tested repeatedly after doing this, and wrapping ISNULL around the sums still left me with the same results.
