Update multiple records SQL with condition (FIFO) - sql

Question

I am sorry before if that title doesn't represent my problem here.
The scenario:
I do outbound 5 items for ItemA
Table FIFO:
| date | item | inbound | outbound |
| 13/11/2015 | itemA | 2 | |
| 15/11/2015 | itemA | 8 | |
My UPDATE script's now (wrong):
| date | item | inbound | outbound |
| 13/11/2015 | itemA | 2 | 5 |
| 15/11/2015 | itemA | 8 | |
The expected result (right):
| date | item | inbound | outbound |
| 13/11/2015 | itemA | 2 | 2 |
| 15/11/2015 | itemA | 8 | 3 |
I have using SQL Server 2008. My script only UPDATE the first row. How to achieve this with SQL?
I am create the scenario on fiddle here. I don't know some script give an error there but in SQL Server is work.
Thank in advance

Answer 1

I think you need to process record by record. Hope the following code helps you to find the logic.
Assumption only one record per date and there will be inbound for all the items.
WHILE #ItemCount>0
BEGIN
SELECT TOP 1 #dat=date,#inbound=inbound FROM FIFO WHERE item='iteamA' AND outbound IS NULL ORDER BY date ASC
IF(#inbound <= #ItemCount)
BEGIN
UPDATE FIFO SET outbound=#inbound WHERE item='iteamA' and date=#dat
ELSE
UPDATE FIFO SET outbound=#ItemCount WHERE item='iteamA' and date=#dat
END
SET #ItemCount=#ItemCount-#inbound
END