Need to use a nested cursor and getting "invalid object name" - sql-server-2008

Question

First, let me state right off that I'm well aware that cursors are generally evil and shouldn't be used - I'm all about using sets, but just couldn't come up with a set-based solution to this particular problem. If you tell me to go do some set-based operations, well, I'm all for it, if you can tell me how you'd code this particular problem.
Basically, I've got a number of stock items for which I need to make purchases. I want to make purchases based upon the cheapest available price, where I know the suppliers' prices and their stock levels. There's also a pack-size issue in here, wherein I want to buy by pack-size if possible.
I've already pulled a list of the things I need to purchase into #needorders, and suppliers' stock levels and prices into #orderedprices. Below I'm iterating through cursor CUR_NEEDED and creating a secondary cursor CUR_AVAILABLE:
DECLARE CUR_NEEDED CURSOR LOCAL SCROLL_LOCKS
FOR
SELECT GoodID
, ConditionID
, QuantityToShip
, OrderStatusID
, RetailerID
, PackSize
FROM #needorders
ORDER BY GoodID
, ConditionID
, PurchaseDate DESC
FOR UPDATE
OPEN CUR_NEEDED
FETCH NEXT FROM CUR_NEEDED INTO #GoodID, #ConditionID, #QuantityToShip, #OrderStatusID, #RetailerID, #PackSize
WHILE ##FETCH_STATUS = 0
BEGIN
DECLARE CUR_AVAILABLE CURSOR LOCAL SCROLL_LOCKS
FOR
SELECT SupplierStocklistItemID
, SupplierID
, StockLevel
, SupplierCurrencyID
, CostPrice
FROM #orderedprices
WHERE #orderedprices.GoodID = #GoodID
AND #orderedprices.ConditionID = #ConditionID
AND #orderedprices.StockLevel > 0
ORDER BY #orderedprices.PriceRank
FOR UPDATE
OPEN CUR_AVAILABLE
FETCH NEXT FROM CUR_AVAILABLE INTO #SupplierStocklistItemID, #SupplierID, #StockLevel, #SupplierCurrencyID, #CostPrice
WHILE ##FETCH_STATUS = 0
BEGIN
/*
Buy as many #PackSize as we need to cover how many we require, unless the supplier
only has a certain number, in which case buy that number.
E.g., need 14, pack size 5, 2 suppliers
Supplier A has 11
Supplier B has 40
Buy 9 from Supplier A, with our remaining need being 3.
Buy 5 from supplier B, with our remaining need being -2
*/
--feed rows into #supplierpurchasesbase while #StockLevel > 0
--Figure out how many we need to buy, based upon PackSize
IF #QuantityToShip % #PackSize > 0
BEGIN
SET #Buy = #QuantityToShip - #QuantityToShip % #PackSize + #PackSize
END
ELSE
BEGIN
SET #Buy = #QuantityToShip
END
IF #StockLevel < #Buy
BEGIN
--PRINT 'Supplier only has ' + CAST(#StockLevel AS VARCHAR) + ' for us to buy.'
SET #Buy = #StockLevel
END
INSERT INTO #supplierpurchasesbase (
GoodID
, ConditionID
, SupplierStocklistItemID
, Quantity
, SupplierID
, SupplierCurrencyID
, CostPrice
, RetailerID )
SELECT #GoodID
, #ConditionID
, #SupplierStocklistItemID
, #Buy
, #SupplierID
, #SupplierCurrencyID
, #CostPrice
, #RetailerID
--update #QuantityToShip & the row in CUR_AVAILABLE
IF #StockLevel <= #Buy
BEGIN
UPDATE CUR_AVAILABLE
SET StockLevel = #StockLevel - #Buy
WHERE CURRENT OF CUR_AVAILABLE
SET #QuantityToShip = 0
END
ELSE
BEGIN
UPDATE CUR_AVAILABLE
SET StockLevel = 0
WHERE CURRENT OF CUR_AVAILABLE
SET #QuantityToShip = #QuantityToShip - #Buy
END
--update the stocklevel so we don't see the thing again if we've used it up.
IF #QuantityToShip = 0 --Don't need any more
BEGIN
UPDATE CUR_NEEDED
SET OrderStatusID = #StatusPendingPO
WHERE CURRENT OF CUR_NEEDED
BREAK
END
ELSE --Need more, move next, if we can
FETCH NEXT FROM CUR_AVAILABLE INTO #SupplierStocklistItemID, #SupplierID, #StockLevel, #SupplierCurrencyID, #CostPrice
END
CLOSE CUR_AVAILABLE
DEALLOCATE CUR_AVAILABLE
FETCH NEXT FROM CUR_NEEDED INTO #GoodID, #ConditionID, #QuantityToShip, #OrderStatusID, #RetailerID, #PackSize
END
CLOSE CUR_NEEDED
DEALLOCATE CUR_NEEDED
The problem I'm running into is that I get I'm getting the error
Invalid object name 'CUR_AVAILABLE'.
when I'm attempting to update CURRENT OF CUR_AVAILABLE.
I've tried defining the CUR_AVAILABLE cursor as #CUR_AVAILABLE but get a different error. I've tried defining the CUR_AVAILABLE cursor outside of the WHILE loop of CUR_NEEDED, I've tried not closing / deallocating the cursor, etc. None of this seems to work.
Any ideas where I'm going wrong, here (other than not using sets, unless you've got a set-based solution)?

Answer 1

The following query uses a recursive CTE and, therefore, can't be considered a truly set-based solution. Nevertheless, I would still expect it to perform better than your two cursors (or to be worth trying, at the very least):
WITH buys (
GoodID,
ConditionID,
SupplierStocklistItemID,
Quantity,
SupplierID,
SupplierCurrencyID,
CostPrice,
RetailerID,
PriceRank,
RemainingNeed,
PackSize
)
AS (
SELECT
GoodID,
ConditionID,
SupplierStocklistItemID = 0,
Quantity = 0,
SupplierID = 0,
SupplierCurrencyID = 0,
CostPrice = CAST(0.00 AS decimal(10,2)),
RetailerID,
PriceRank = 0,
RemainingNeed = QuantityToShip,
PackSize
FROM #needorders
UNION ALL
SELECT
p.GoodID,
p.ConditionID,
p.SupplierStockListItemID,
Quantity = y.CurrentBuy,
p.SupplierID,
p.SupplierCurrencyID,
p.CostPrice,
b.RetailerID,
p.PriceRank,
RemainingNeed = b.RemainingNeed - y.CurrentBuy,
b.PackSize
FROM #orderedprices p
INNER JOIN buys b ON p.GoodID = b.GoodID
AND p.ConditionID = b.ConditionID
AND p.PriceRank = b.PriceRank + 1
CROSS APPLY (
SELECT RemainingNeedAdjusted =
(b.RemainingNeed + b.PackSize - 1) / b.PackSize * b.PackSize
) x
CROSS APPLY (
SELECT CurrentBuy = CASE
WHEN x.RemainingNeedAdjusted > p.StockLevel
THEN p.StockLevel
ELSE x.RemainingNeedAdjusted
END
) y
WHERE p.StockLevel > 0
AND b.RemainingNeed > 0
)
SELECT
GoodID,
ConditionID,
SupplierStocklistItemID,
Quantity,
SupplierID,
SupplierCurrencyID,
CostPrice,
RetailerID
FROM buys
WHERE PriceRank > 0
ORDER BY
GoodID,
ConditionID,
PriceRank
Basically, the CTE forms the rows almost identical to those your query is inserting into #supplierpurchasesbase, except it additionally features auxiliary columns serving as kind of internal variables. (They are not pulled by the final SELECT, though.)
The anchor part forms a set of 0-quantity records based on the #needordered table, together with the initial values for the auxiliary columns. The recursive part contains all the logic: calculates the quantity to buy, updates the "remaining need" quantity for the next iteration, checks whether the next iteration is needed.
Certain assumptions have been made, and I hope you'll be able find your way around them if they do not match your real situation. For instance, quantities, pack sizes are assumed to be integer, and part of the logic relies on that, because it uses integral division. It is also assumed that PriceRank is a sequence of integers starting from 1, unique per (GoodID, ConditionID).
This script, as well as a minimal test setup, can be found, tested, modified, and tested on SQL Fiddle.

Answer 2

The problem was twofold: The update syntax should not be:
UPDATE CUR_AVAILABLE
SET StockLevel = #StockLevel - #Buy
WHERE CURRENT OF CUR_AVAILABLE
Rather, the syntax should be:
UPDATE #orderedprices
SET StockLevel = #StockLevel - #Buy
WHERE CURRENT OF CUR_AVAILABLE
Also, in order to be updatable, the temp table needed to have a primary key:
ALTER TABLE #orderedprices ADD CONSTRAINT PRIMARY KEY CLUSTERED (RowCtr)
Lesson learned, I guess, but it certainly took me a fair bit of grief to find the solution!