Allocated Stock Qty based on Order Qty in SQL Server 2008 - sql-server

Question

I have a query below to allocated stock qty to match order qty based on order type. The problem is the stock qty is not updated.
DECLARE #tblOrder TABLE
(DealerCode NVARCHAR(50),
PartCode NVARCHAR(50),
OrderQty INT,
OrderType NVARCHAR(50)
)
INSERT INTO #tblOrder
( DealerCode,
PartCode,
OrderQty,
OrderType )
VALUES ('D1','A',19,'Urgent'),
('D2','B',10,'Normal'),
('D3','C',11,'HotLine'),
('D1','D',20,'Normal'),
('D2','E',12,'Normal'),
('D1','D',40,'Normal');
DECLARE #tblStock TABLE
(PartCode NVARCHAR(50),
StockQty INT)
INSERT INTO #tblStock
( PartCode,
StockQty)
VALUES ('A',20),
('B',15),
('C',9),
('D',30),
('E',0)
;WITH ordertemp AS (
select ord.dealercode,
ord.partcode,
ord.orderqty,
ord.ordertype,
RANK() OVER (ORDER BY case ord.ordertype when 'HotLine' then 1 when 'Urgent' then 2 else 3 end, ord.partcode, ord.dealercode) 'StockPriority',
sto.stockqty 'InitialStock'
from #tblorder ord
left outer join #tblstock sto
on ord.partcode = sto.partcode )
SELECT
Orders.dealercode,
Orders.partcode,
CASE WHEN Backlog.PriorQty > Orders.InitialStock THEN 0
ELSE Orders.InitialStock - Backlog.PriorQty END 'Stock',
Orders.orderqty,
CASE WHEN Backlog.PriorQty + Orders.OrderQty < Orders.InitialStock THEN Orders.OrderQty
WHEN Backlog.PriorQty > Orders.InitialStock THEN 0
ELSE Orders.InitialStock - Backlog.PriorQty END 'Allocated',
Orders.ordertype
FROM
ordertemp Orders
INNER JOIN
(
SELECT A.stockpriority, A.partcode, ISNULL(SUM(B.orderqty),0) 'PriorQty'
from ordertemp A
LEFT OUTER JOIN ordertemp B
on A.partcode = B.partcode
and A.stockpriority > B.stockpriority
group by A.stockpriority, A.partcode ) Backlog
ON Orders.stockpriority = Backlog.stockpriority
ORDER BY Orders.StockPriority
I got result:
dealercode partcode stock orderqty allocated ordertype
D3 C 9 11 9 HotLine
D1 A 20 19 19 Urgent
D2 B 15 10 10 Normal
D1 D 30 20 20 Normal
D1 D 30 40 30 Normal
D2 E 0 12 0 Normal
Actually, the stock (30) of partcode 'D' must be remain 10 after allocated 20.
Any idea please?

Answer 1

The Reason you get stock 30 is because your are using RANK for prioritization. RANK will allocate the same number to two order records if they have the same stock priority as defined by your condition ORDER BY case ord.ordertype when 'HotLine' then 1 when 'Urgent' then 2 else 3 end, ord.partcode, ord.dealercode. If you check the output of ordertemp you will see
dealercode partcode orderqty ordertype StockPriority InitialStock
D3 C 11 HotLine 1 9
D1 A 19 Urgent 2 20
D2 B 10 Normal 3 15
D1 D 20 Normal 4 30
D1 D 40 Normal 4 30
D2 E 12 Normal 6 0
Notice that the StockPriority of partcode D is 4 for both rows 4 and 5.
You can fix this by using ROW_NUMBER() instead of RANK() . You can also add orderqty in ROW_NUMBER() to specify if you want higher priority for smaller/larger orders if they have the same ordertype, partcode and dealercode.
Query with ROW_NUMBER()
DECLARE #tblOrder TABLE
(DealerCode NVARCHAR(50),
PartCode NVARCHAR(50),
OrderQty INT,
OrderType NVARCHAR(50)
)
INSERT INTO #tblOrder
( DealerCode,
PartCode,
OrderQty,
OrderType )
VALUES ('D1','A',19,'Urgent'),
('D2','B',10,'Normal'),
('D3','C',11,'HotLine'),
('D1','D',20,'Normal'),
('D2','E',12,'Normal'),
('D1','D',40,'Normal');
DECLARE #tblStock TABLE
(PartCode NVARCHAR(50),
StockQty INT)
INSERT INTO #tblStock
( PartCode,
StockQty)
VALUES ('A',20),
('B',15),
('C',9),
('D',30),
('E',0)
;WITH ordertemp AS (
select ord.dealercode,
ord.partcode,
ord.orderqty,
ord.ordertype,
ROW_NUMBER() OVER (ORDER BY case ord.ordertype when 'HotLine' then 1 when 'Urgent' then 2 else 3 end, ord.partcode, ord.dealercode) 'StockPriority',
sto.stockqty 'InitialStock'
from #tblorder ord
left outer join #tblstock sto
on ord.partcode = sto.partcode )
SELECT
Orders.dealercode,
Orders.partcode,
CASE WHEN Backlog.PriorQty > Orders.InitialStock THEN 0
ELSE Orders.InitialStock - Backlog.PriorQty END 'Stock',
Orders.orderqty,
CASE WHEN Backlog.PriorQty + Orders.OrderQty < Orders.InitialStock THEN Orders.OrderQty
WHEN Backlog.PriorQty > Orders.InitialStock THEN 0
ELSE Orders.InitialStock - Backlog.PriorQty END 'Allocated',
Orders.ordertype
FROM
ordertemp Orders
INNER JOIN
(
SELECT A.stockpriority, A.partcode, ISNULL(SUM(B.orderqty),0) 'PriorQty'
from ordertemp A
LEFT OUTER JOIN ordertemp B
on A.partcode = B.partcode
and A.stockpriority > B.stockpriority
group by A.stockpriority, A.partcode ) Backlog
ON Orders.stockpriority = Backlog.stockpriority
ORDER BY Orders.StockPriority

Answer 2

He's quite right above - when you first posted I had made the assumption you'd only have one entry per supplier per part / priority rather than duplicates :)
Note if you added orderquantity you would still face a problem if you had 2 entries with the same quantity in each.