Query - display zero where null in one column and select sum of two columns where not null in next column - sql

Question

I need to display a zero where "Silo Wt" is null, and display the sum of the two values in the Total column even if "Silo Wt" is null.. may not require any changes if I can get a zero in the Silo column
SELECT DISTINCT (coffee_type) AS "Coffee_Type",
(SELECT ItemName
FROM [T01_Item_Name_TBL]
WHERE Item = B.Coffee_Type) AS "Description",
(SELECT COUNT(Green_Inventory_ID)
FROM [Green_Inventory] AS A
WHERE A.Coffee_Type = B.Coffee_Type
AND current_Quantity > 0) AS "Current Units",
SUM((Unit_Weight) * (Current_Quantity)) AS "Green Inv Wt",
(SELECT SUM(TGWeight)
FROM [P04_Green_STotal_TBL] AS C
WHERE TGItem = Coffee_type) AS "Silo Wt",
(SUM((Unit_Weight) * (Current_Quantity)) +
(SELECT SUM(TGWeight)
FROM [P04_Green_STotal_TBL] AS C
WHERE TGItem = Coffee_type)) AS Total
FROM
[Green_Inventory] AS B
WHERE
Pallet_Status = 0
GROUP BY
Coffee_Type
SS of query results now

Answer 1

You just need to wrap them in ISNULL.
However, your query could do with some serious cleanup and simplification:
DISTINCT makes no sense as you are grouping by that column anyway.
Two of the subqueries can be combined using OUTER APPLY, although this requires moving the grouped Green_Inventory into a derived table.
Another subquery, the self-join on Green_Inventory, can be transformed into conditional aggregation.
Not sure whether I've got the logic right, as the subquery did not have a filter on Pallet_Status, but it looks like you would also need to move that condition into conditional aggregation for the SUM, and use a HAVING. It depends exactly on your requirements.
Don't use quoted table or column names unless you have to.
Use meaningful table aliases, rather than A B C.
Specify table names when referencing columns, especially when using subqueries, or you might get unintended results.
SELECT
gi.Coffee_Type,
(SELECT ItemName
FROM T01_Item_Name_TBL AS n
WHERE n.Item = gi.coffee_Type
) AS Description,
ISNULL(gst.TGWeight, 0) AS SiloWt,
ISNULL(gi.GreenInvWt, 0) + ISNULL(gst.TGWeight, 0) AS Total
FROM (
SELECT
gi.Coffee_Type,
COUNT(CASE WHEN gi.current_Quantity > 0 THEN 1 END) AS CurrentUnits,
SUM(CASE WHEN gi.Pallet_Status = 0 THEN gi.Unit_Weight * gi.Current_Quantity END) AS GreenInvWt
FROM
Green_Inventory AS gi
GROUP BY
gi.Coffee_Type
HAVING
SUM(CASE WHEN gi.Pallet_Status = 0 THEN gi.Unit_Weight * gi.Current_Quantity END) > 0
) AS gi
OUTER APPLY (
SELECT SUM(gst.TGWeight) AS TGWeight
FROM P04_Green_STotal_TBL AS gst
WHERE gst.TGItem = gi.Coffee_Type
) AS gst;