FIFO in pl/sql query or procedure

Question

Hi,
I have two tables:
1)Table of recieved items
create table receipts
(item_id number(5),
recieved_date date,
recieved_quantity number,
receipt_id number(5));
insert into receipts(item_id, recieved_date, recieved_quantity, receipt_id)
values(668, '29/12/10', 400, 441);
insert into receipts(item_id, recieved_date, recieved_quantity, receipt_id)
values(668, '29/12/10', 100, 442);
insert into receipts(item_id, recieved_date, recieved_quantity, receipt_id)
values(668, '03/02/11', 150, 444);2)Table of sold items
create table deliveries
(item_id number(5),
delivered_date date,
delivered_quantity number,
delivery_id number(5));
insert into deliveries(item_id, delivered_date, delivered_quantity, delivery_id)
values(668, '01/02/11', 10, 1301);
insert into deliveries(item_id, delivered_date, delivered_quantity, delivery_id)
values(668, '02/02/11', 450, 1303);
insert into deliveries(item_id, delivered_date, delivered_quantity, delivery_id)
values(668, '08/02/11', 15, 1305);
insert into deliveries(item_id, delivered_date, delivered_quantity, delivery_id)
values(668, '09/02/11', 90, 1306);I need to track down from which batch goods are taken (for each delivery) using FIFO method.
FIFO priorities are RECIEVED_DATE, RECEIPT_ID for INs and DELIVERED_DATE, DELIVERY_ID for OUTs.
Desired output should be something like this:
{noformat}
ITEM_ID          DELIVERED_DATE  DELIVERED_QUANTITY      DELIVERY_ID     FROM_RECEIPT    STOCK_QUANTITY(*)
668          01/02/11     10               1301          441          390
668          02/02/11     390(**)               1303          441          0
668          02/02/11     60(**)               1303          442          40
668          08/02/11     15               1305          442          25
668          09/02/11     25(**)               1306          442          0
668          09/02/11     65(**)               1306          443          85
{noformat}(*)Where STOCK_QUANTITY is the remaining quantity from that batch at the moment after according delivery amount deduction.
(**)If the delivery gets the goods from different batches, the row should be split to display the amount taken from each batch.
How can I make pl/sql query/procedure to track down this?
Any help is very appreciated.
DB version is: Oracle Database 11g Enterprise Edition Release 11.1.0.6.0
Thank you,
Nikita

Answer 1

Hi, Nikita,
Thanks for posting the CREATE TABLE and INSERT statements; that's very helpful.
Use the analytic SUM functuion to get a running total of how much has been receeived and delivered to date. I did this in the sub-queries deliveries_rt and reciepts_rt:
WITH     receipts_rt     AS
     SELECT     item_id
     ,     received_date
     ,     received_quantity
     ,     SUM (received_quantity) OVER ( PARTITION BY  item_id
                                    ORDER BY          received_date
                                ,               receipt_id
                              )      AS received_total
     ,     receipt_id
     FROM    receipts
,     deliveries_rt     AS
     SELECT     item_id
     ,     delivered_date
     ,     delivered_quantity
     ,     SUM (delivered_quantity) OVER ( PARTITION BY  item_id
                                     ORDER BY      delivered_date
                                 ,                delivery_id
                              )      AS delivered_total
     ,     delivery_id
     FROM    deliveries
SELECT       d.item_id
,       d.delivered_date
,       LEAST ( received_total  + delivered_quantity - delivered_total
            , delivered_total + received_quantity  - received_total
          , delivered_quantity    -- *****  See correction, below  *****
          )          AS delivered_quantity
,       d.delivery_id
,       r.receipt_id          AS from_receipt
,       GREATEST ( received_total - delivered_total
               , 0
             )          AS stock_quantity
FROM       deliveries_rt     d
JOIN       receipts_rt     r  ON     d.item_id        = r.item_id
                    AND     d.delivered_total  > r.received_total  - r.received_quantity
                  AND     r.received_total   > d.delivered_total - d.delivered_quantity
ORDER BY  d.item_id
,            d.delivered_date
,       d.delivery_id
,            r.received_date
,       r.receipt_id
;What role does item_id play in this problem? I made a guess, but guessing isn't a very good way to solve problems.
It may help to think of each row as having a low running total (or low_rt, the total quantity up to, but NOT including the current row) and a high running total (high_rt, the total qualntity up to AND including the current row). In the sub-queries above, I only computed the high_rt, since it's easy enough to get the low_rt from that by subtraction.
Each row in the deliveries table will be joined to a row in the receipts table if the running totals overlap, that is, if the high_rt of each row is greaterr than the low_rt of the other.
Delivered_quantity is the minimum of the high_rt from either table minus the low_rt of the other, but it can never be greater than the delivered_quantity.
Edited by: Frank Kulash on Mar 3, 2011 10:06 AM
Brief explanation added.
Edited by: Frank Kulash on Apr 23, 2013 12:56 PM
<H3>Correction</H3>
The computation of delivered_quantity in the main query should have 1 more argument to LEAST, like this:
,       LEAST ( r.received_total  + d.delivered_quantity - d.delivered_total
            , d.delivered_total + r.received_quantity  - r.received_total
          , d.delivered_quantity
          , r.received_quantity               -- ***  Added  ***
          )          AS delivered_quantityThanks to Jean Marie Delhaze ( {message:id=10980754} below) for finding and correcting my mistake.