Get most recent Price for each Item - sql

Question

I have a table:
ItemID PurchaseDate Price
001 03/17/2013 19.00
002 03/17/2013 14.00
001 03/18/2013 13.00
002 03/18/2013 15.00
001 03/19/2013 17.00
003 03/19/2013 19.00
I need to write a SQL query to get the Price corresponding to the latest PurchaseDate for each ItemID.
Entries in table might not necessarily be entered ordered by date
Like this:
ItemID PurchaseDate Price
001 03/19/2013 17.00
002 03/18/2013 15.00
003 03/19/2013 19.00

Answer 1

The idea behind the subquery is it separately gets the latest PurchaseDate for each ItemID. The result of the subquery is then joined back on the table provided that it matches on two conditions: ItemID and PurchaseDate.
SELECT a.*
FROM TableName a
INNER JOIN
(
SELECT ItemID, MAX(PurchaseDate) max_date
FROM TableName
GROUP BY ItemID
) b ON a.ItemID = b.ItemID AND
a.PurchaseDate = b.max_date

Answer 2

-- WITH clause, works with Oracle.
-- I added this clause to dynamically run the SELECT statement without any DDL.
-- Ignore this section for use on MS Access
WITH v AS (
SELECT 001 ItemID, TO_DATE('03/17/2013', 'MM/DD/YYYY') PurchaseDate, 19.00 Price FROM dual
UNION ALL
SELECT 002, TO_DATE('03/17/2013', 'MM/DD/YYYY'), 14.00 FROM dual
UNION ALL
SELECT 001, TO_DATE('03/18/2013', 'MM/DD/YYYY'), 13.00 FROM dual
UNION ALL
SELECT 002, TO_DATE('03/18/2013', 'MM/DD/YYYY'), 15.00 FROM dual
UNION ALL
SELECT 001, TO_DATE('03/19/2013', 'MM/DD/YYYY'), 17.00 FROM dual
UNION ALL
SELECT 003, TO_DATE('03/19/2013', 'MM/DD/YYYY'), 19.00 FROM dual
)
-- The WITH clause was upto here.
-- Below starts the main query which works on most platforms including MS Access.
-- I have referenced to the same table "v" two times - v_in and v_out.
-- You will need to change the "v" with your table name.
SELECT v_out.itemid, v_out.purchasedate, v_out.price
FROM v v_out
WHERE EXISTS (SELECT 1
FROM v v_in
WHERE v_in.itemid = v_out.itemid
GROUP BY v_in.itemid
HAVING MAX(v_in.purchasedate) = v_out.purchasedate)
ORDER BY v_out.itemid
;