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 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!