MS-Access Get price of product at certain order date

Question

I have a table filled with purchase prices, like this:

sku                   price    btw   startdate
PCR-CA5425023181515   21,17 €   1    01/01/2009
PCR-CA5425023181515  999,00 €   1    06/06/2009
PCR-CA5425023181515  444,00 €   4    09/07/2009
PCR-CA5425023181515  100,00 €   4    10/08/2009

I have another table filled with orders, like this:

sku                  quantity   orderdate
PCR-CA5425023181515     5       01/05/2009
PCR-CA5425023181515    10       01/12/2009
PCR-CA5425023181515    10       24/12/2009

My goal is to get every purchase price per order from that date. (For example: when I ordered the product on the first of may (01/05) it cost 21,17 euros. When I ordered it on the first of december (01/12) it cost 100,00 euros.)

I've been struggling with this for the past hour, but haven't found anything useful yet.

Answer 1

SELECT
     O.sku,
     O.qty,
     PP.price
FROM
     Orders O
INNER JOIN Purchase_Prices PP ON
     PP.sku = O.sku AND
     PP.start_date <= O.order_date
WHERE
     NOT EXISTS
     (
          SELECT
               *
          FROM
                Purchase_Prices PP2
          WHERE
                PP2.sku = PP.sku AND
                PP2.start_date <= O.order_date AND
                PP2.start_date > PP.start_date
     )

Alternatively:

SELECT
     O.sku,
     O.qty,
     PP.price
FROM
     Orders O
INNER JOIN Purchase_Prices PP ON
     PP.sku = O.sku AND
     PP.start_date <= O.order_date
LEFT OUTER JOIN Purchase_Prices PP2 ON
     PP2.sku = O.sku AND
     PP2.start_date <= O.order_date AND
     PP2.start_date > PP.start_date
WHERE
     PP2.sku IS NULL