Get most recent Price for each Item

问题

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

回答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

回答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
;

来源：https://stackoverflow.com/questions/15495133/get-most-recent-price-for-each-item

标签

sql

ms-access

greatest-n-per-group