Question

I have a problem getting the right “Price” for a product based on Effectivity date.

Example, I have 2 tables:

a. “Transaction” table –> this contains the products ordered, and
b. “Item Master” table –> this contains the product prices and effectivity dates of those prices

Inside the Trasaction table:

INVOICE_NO  INVOICE_DATE    PRODUCT_PKG_CODE    PRODUCT_PKG_ITEM
1234            6/29/2009      ProductA            ProductA-01
1234            6/29/2009      ProductA            ProductA-02
1234            6/29/2009      ProductA            ProductA-03


Inside the "Item_Master" table:

PRODUCT_PKG_CODE    PRODUCT_PKG_ITEM    PRODUCT_ITEM_PRICE  EFFECTIVITY_DATE
ProductA            ProductA-01          25                  6/1/2009
ProductA            ProductA-02          22                  6/1/2009
ProductA            ProductA-03          20                  6/1/2009
ProductA            ProductA-01          15                  5/1/2009
ProductA            ProductA-02          12                  5/1/2009
ProductA            ProductA-03          10                  5/1/2009
ProductA            ProductA-01          19                  4/1/2009
ProductA            ProductA-02          17                  4/1/2009
ProductA            ProductA-03          15                  4/1/2009

In my report, I need to display the Invoices and Orders, 
as well as the Price of the Order Item which was effective 
at the time it was paid (Invoice Date).
My query looks like this (my source db is Oracle):

SELECT   T.INVOICE_NO,
     T.INVOICE_DATE,
     T.PRODUCT_PKG_CODE,
     T.PRODUCT_PKG_ITEM,
     P.PRODUCT_ITEM_PRICE    FROM   TRANSACTION T,
     ITEM_MASTER P    WHERE   T.PRODUCT_PKG_CODE = P.PRODUCT_PKG_CODE
     AND T.PRODUCT_PKG_ITEM = P.PRODUCT_PKG_ITEM
     AND P.EFFECTIVITY_DATE <= T.INVOICE_DATE
     AND T.INVOICE_NO = '1234';

…which shows 2 prices for each item.
I did some other different query styles
but to no avail, so I decided
it’s time to get help. 🙂
Thanks to any of you who can
share your knowledge. –CJ–

p.s. Sorry, my post doesn’t even look right! 😀

Answer 1

Analytics is your friend. You can use the FIRST_VALUE() function, for example, to get all the product_item_prices for the given product, sort by effectivity_date (descending), and just pick the first one. You’ll need a DISTINCT as well so that only one row is returned for each transaction.

SELECT   DISTINCT
     T.INVOICE_NO,
     T.INVOICE_DATE,
     T.PRODUCT_PKG_CODE,
     T.PRODUCT_PKG_ITEM,
     FIRST_VALUE(P.PRODUCT_ITEM_PRICE)
       OVER (PARTITION BY T.INVOICE_NO, T.INVOICE_DATE,
                         T.PRODUCT_PKG_CODE, T.PRODUCT_PKG_ITEM
            ORDER BY P.EFFECTIVITY_DATE DESC)
        as PRODUCT_ITEM_PRICE
FROM   TRANSACTION T,
     ITEM_MASTER P    
WHERE   T.PRODUCT_PKG_CODE = P.PRODUCT_PKG_CODE
     AND T.PRODUCT_PKG_ITEM = P.PRODUCT_PKG_ITEM
     AND P.EFFECTIVITY_DATE <= T.INVOICE_DATE
     AND T.INVOICE_NO = '1234';