On Mon, 9 Sep 2002 18:08:21 +1000
"jack" <datactrl@tpg.com.au> wrote:
> Dima
> My question is that I want to produce ALL the lastest 3 records for EACH
> itemNo and supplier.
>
> Jack
I often use the next query for ranking, which is equivalent to Oracle's
PARTITION BY(). It isn't influenced by what kind of data your table has;
it only depends on the result of sorting
CREATE TEMP SEQUENCE seq_purchase;
SELECT t5.item_no, t5.supplier, t5.purchase_date, t5.price, t5.qty, t5.i - t3.n + 1 AS rank
FROM (SELECT t2.item_no, t2.supplier, min(t2.i) AS n FROM (SELECT t1.*, nextval('seq_purchase') - 1 AS i
FROM (SELECT (SELECT setval('seq_purchase',1)), * FROM purchase ORDER BY
item_no,supplier, purchase_date desc ) AS t1 LIMIT ALL ) AS t2 GROUP BY
t2.item_no,t2.supplier ) AS t3, (SELECT t4.*, nextval('seq_purchase') - 1 AS i FROM (SELECT (SELECT
setval('seq_purchase',1)),* FROM purchase ORDER BY item_no, supplier, purchase_date DESC
) AS t4 LIMIT ALL ) AS t5
WHERE t3.item_no = t5.item_no AND t3.supplier = t5.supplier AND t5.i - t3.n + 1 <= 3
;
Regards,
Masaru Sugawara