From: | "Claus Guttesen" <kometen(at)gmail(dot)com> |
---|---|
To: | "David Garamond" <davidgaramond(at)gmail(dot)com> |
Cc: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: query: last N price for each product? |
Date: | 2008-07-04 12:44:22 |
Message-ID: | b41c75520807040544l3750718cp55fc65a1a633e830@mail.gmail.com |
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Thread: | |
Lists: | pgsql-sql |
> The query for "latest price for each product" goes like this (which I
> can grasp quite easily):
>
> SELECT * FROM price p1
> WHERE ctime=(SELECT MAX(ctime) FROM price p2 WHERE p1.product_id=p2.product_id)
>
> or:
>
> SELECT * FROM price p1
> WHERE NOT EXISTS (SELECT * FROM price p2 WHERE
> p1.product_id=p2.product_id AND p1.ctime < p2.ctime)
>
> but how do yo query for "latest 3 prices for each product"? The
> "price" table contains current price as well as price histories.
Will this work?
SELECT * FROM price p1
WHERE ctime int (SELECT ctime FROM price p2 WHERE
p1.product_id=p2.product_id order by ctime desc limit 3)
--
regards
Claus
When lenity and cruelty play for a kingdom,
the gentlest gamester is the soonest winner.
Shakespeare
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