query replace blank - sql

Question

My query draws the total cost from two other queries and then adds these together to generate a job cost total. My issue is that when a job is entered and the query runs its magic in the background, dependant on the job means that one field may not contain any cost information. I believe it to be because of these empty cells that the totals do not populate correctly and thus will need to replace the blanks with £0.
https://i.stack.imgur.com/zcnk2.png
https://i.stack.imgur.com/OWJdX.png
SELECT tblMaintenanceLog.LogID, Last(QIntTotals.IntTotal) AS LastOfIntTotal, Last(QExtPartsTotalsComp.SumOfSumOfEXTPCost) AS LastOfSumOfSumOfEXTPCost, [IntTotal]+[SumOfSumOfEXTPCost] AS Expr1
FROM (tblMaintenanceLog LEFT JOIN QIntTotals ON tblMaintenanceLog.LogID = QIntTotals.INTJobID) LEFT JOIN QExtPartsTotalsComp ON tblMaintenanceLog.LogID = QExtPartsTotalsComp.EXTPJobID
GROUP BY tblMaintenanceLog.LogID, [IntTotal]+[SumOfSumOfEXTPCost]
ORDER BY tblMaintenanceLog.LogID;
I have tried an if statement to replace blanks with 0 and also the Nz function without any avail. However, I could just be entering it in wrong as I am still relatively new to VBA and SQL so any help would be greatly appreciated!
Thank you all :)

Answer 1

You can use COALESCE in this case.
SELECT tblMaintenanceLog.LogID , COALESCE(NULLIF(Last(QIntTotals.IntTotal),''),0) AS LastOfIntTotal, Last(QExtPartsTotalsComp.SumOfSumOfEXTPCost) AS LastOfSumOfSumOfEXTPCost, [IntTotal]+[SumOfSumOfEXTPCost] AS Expr1
FROM (tblMaintenanceLog LEFT JOIN QIntTotals ON tblMaintenanceLog.LogID = QIntTotals.INTJobID) LEFT JOIN QExtPartsTotalsComp ON tblMaintenanceLog.LogID = QExtPartsTotalsComp.EXTPJobID
GROUP BY tblMaintenanceLog.LogID, [IntTotal]+[SumOfSumOfEXTPCost]
ORDER BY tblMaintenanceLog.LogID;

Answer 2

I have the answer!!
Iif(Last(QIntTotals.IntTotal) is null, 0, Last(QIntTotals.IntTotal))
I cant thank you enough for your help ppijnenburg! I didn't realise how to properly add stuff in SQL until you shown me that! You have saved me much heartache!!!! Thank you :)