Question

I´ve been struggling for several days with a problem. I have a couple of tables in an Oracle DB (10g), one that shows a list of orders sorted by priority and the other an inventory of products. What I want to do is assign the available products to the orders based on the priority. My questions are:

• Each order will receive only one product. How can I select only the orders that can receive a product based on the available existence?
• To make the procedure more efficient, is there a way of storing the inventory changes while selecting the products, and apply the update at the end of the procedure?

Both tables will have thousands of items, so I think a PL/SQL stored procedure would be more efficient.

Thanks for your time and help.

PS: This is an example of my tables.

Orders
-------------------------------------------
| ID      |  Priority     |     Product
-------------------------------------------
| Order1  |    50         |        1
| Order7  |    48         |        3
| Order3  |    45         |        1
| Order2  |    40         |        1
| Order9  |    30         |        2
| Order4  |    15         |        3


 Inventory
-------------------------------------------
| ProductID |  Qty      
-------------------------------------------
| 1         |    2 
| 2         |    4 
| 3         |    1 

After running the stored procedure I need to get the following result and need to update the inventory.

-------------------------------------------
| ID      |  Priority     |     Product
-------------------------------------------
| Order1  |    50         |        1
| Order7  |    48         |        3
| Order3  |    45         |        1
| Order9  |    30         |        2

Updated Inventory
-------------------------------------------
| ProductID |  Qty      
-------------------------------------------
| 1         |    0 
| 2         |    3 
| 3         |    0 

Answer 1

Yep a procedure would be the best way to handle the transaction.

Open a cursor and populate it with your ordered Order table. Loop through the cursor and update the Inventory table as you fulfill the orders.

CREATE OR REPLACE PROCEDURE update_oders (status OUT BOOLEAN)
IS
    CURSOR orders
    IS
          SELECT id, priority, product
            FROM orders
        ORDER BY priority DESC;
BEGIN
    status := FALSE;

    FOR cur_rec IN orders
    LOOP
        BEGIN
            SELECT COUNT ( * )
              INTO inventory_count
              FROM inventory
             WHERE productid = cur_rec.product;

            IF inventory_count > 0
            THEN
                BEGIN
                    UPDATE inventory
                       SET qty = qty - 1
                     WHERE productid = cur_rec.product;

                    INSERT INTO filledorder (id, priority, product)
                        VALUES (id, priority, product);
                EXCEPTION
                    WHEN OTHERS
                    THEN
                        --log error about problem..
                        ROLLBACK;
                END;
            ELSE
                -- log some error or order inventory?
                NULL;
            END IF;
        EXCEPTION
            WHEN NO_DATA_FOUND
            THEN
                --log data;
                NULL;
        END;
    END LOOP;

    COMMIT;
    status := TRUE;
EXCEPTION
    WHEN OTHERS
    THEN
        -- log 
        ROLLBACK;
        status := FALSE;
END;