I am afraid, you misexplained your problem.
Anyway, null problem can by avoided by "coalesce" ( myAmount = coalesce
( (selec sum... ), 0);
Or by adding manually default 0 in sql, or by adding trigger with
default writing 0 to field value.
Fabio Gomes wrote:

>Thanks for the quick reply.
>
>I started to use these procedures on my database, but i m with some
>problems..
>
>I ve altered the table products and added the filed actual_stock on it, then
>i ve created the procedure to sum the added value with the actual stock.
>
>But it isnt working when i have a null value in my actual_stock, like.. if i
>add a new product, and the insert something in the stock _control table it
>doesnt work, but if i have already an actual_stock value in my products
>table, it works.
>
>how can i solve this?
>
>I m using ibwebadmin, and i didnt find how to put a default value (like 0)
>on the actual_stock field.
>
>Thanks in advance :)
>
>On 11/21/05, Adomas Urbanavicius <adomas@...> wrote:
>
>
>> so, add that procedure into you trigger after insert,after delete..
>>wherever
>>execute procedure recalculate_sums(new/old.pro_id);
>>where SP body something like
>>
>>update stocks set amount =
>>
>>(
>>SELECT sum(Quantity) On_Hand
>>FROM StockControl
>>WHERE Pro_Id = :Pro_Id
>>)
>>where
>>Pro_Id = :Pro_Id
>>
>>
>>ps. just make sure about transactions, if two users in same time with
>>same pro_id will work, I think you'll have to make transactions lock
>>wait to update correctly.
>>
>>Fabio Gomes wrote:
>>
>>
>>
>>>Just another question,
>>>
>>>How can i make a function to update the actual_stock after i delete a
>>>
>>>
>>row?
>>
>>
>>>This works when i insert a row:
>>>
>>>CREATE TRIGGER SCI ACTIVE AFTER INSERT AS
>>>BEGIN
>>>UPDATE STOCK
>>>SET ACTUAL_STOCK = ACTUAL_STOCK + NEW.STOCK_ADDED
>>>WHERE PRO_ID = NEW.PRO_ID;
>>>END
>>>
>>>I want to make something like it:
>>>
>>>SELECT Pro_Id, sum(Quantity) On_Hand
>>>
>>>
>>>FROM StockControl
>>
>>
>>>WHERE Pro_Id = :Pro_Id
>>>
>>>I think that i need to make a function that actived after i delete
>>>something, than it sum all the stock for that product and write it on the
>>>actual_stock on the other table.
>>>
>>>is there some way to do it?
>>>
>>>Thanks guys :)
>>>
>>>
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