CF Not Returning Correct Results

I have a column that has both positive and negative numbers and I am trying to seperate those numbers into a seperate column each. My code below is working if each barcode has both a positive and negative number to compare, but errors are thrown such as "can't convert " to a numeric value" if I just have all positive numbers in the colum. Which, in some casees, I will have because I am importing a CSV file. Can anyone help with the code? - Thanks.

<!--- SUM POSITVE QUANTITY --->
<cfquery name="SumPositiveTemp" datasource='inventory'>
SELECT barcode, sum(quantity) as quantitysumPositive
FROM temp
WHERE Quantity > 0 
GROUP BY barcode
</cfquery>

<!--- SUM NEGATIVE QUANTITY --->
    <cfquery name="SumNegativeTemp" datasource='inventory'>
    SELECT barcode, sum(quantity) as quantitysumNegative
    FROM temp
    WHERE Quantity < 0 
    GROUP BY barcode
    </cfquery>
   
<!--- SUBTRACT QUANTITY ISSUED MINUS QUANTITY RECEIVED TO GET QUANTITY SOLD --->
    <cfset QuanitySold = '#SumPositiveTemp.quantitysumPositve-SumNegativeTempquantitysumNegative#'>

<!--- INSERT POSITVIE/NEGATIVE NUMBERS INTO TABLE--->
<cfoutput query="SumPositiveTemp">
    <cfquery name="InsertPositiveIntoCart" datasource="inventory">
   INSERT INTO Cart1 (barcode, QuantityOut, QuantityIn, QuantitySold)
    VALUES (#SumPositiveTemp.barcode#, #SumPositiveTemp.quantitysumPositive#, #SumNegativeTemp.quantitysumNegative#, #QuantitySold#)
    </cfquery>
</cfoutput>