Is Null (Access 2000)

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I have a function that substracts the quantity in the stock in the field called stock in the table Products.It works fine,however i do not want to substract if the stock is Null, and give a message ”
there are no more goods available”.How can i confine the function only if the stock is not Null ?

The function is the following

strSQLBulems = “UPDATE Products SET Stock = Stock – ” & Me.cartons & ” WHERE ProductID=” & Me.Productid

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Your stock should *never* be null because that doesn’t make sense. The least value it should have is zero. Logically it’s impossible to have null anything.

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Thank you very much indeed for your reply.If i subtract with 0 quantities, then i receice minus values.How can i avoid that?I want to substract only when the quantity is not 0

Best regards

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you need to do the calculation first, and test the result with an if-then-else statement of the form
if result >= 0 then
‘ positive result processing
else
‘ negative result processing
end if

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Try something like this:

If lngStock >0 And _
        lngStock>=Me.Cartons Then
   lngNewStock = lngStock - Me.Cartons
Else
  lngNewStock = 0
End If

I don’t see how you can subtract more items than you have in inventory unless your inventory records aren’t being kept current. You shouldn’t be able to remove more cartons from inventory than exist there, so you shouldn’t be coming up with negative numbers.

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