You mean
to list the complete orders table and for each of its records, the
corresponding record on the orders_log with the latest ol_timestamp?
SELECT *
FROM orders_log main
JOIN
(
SELECT orders.*, MAX(orders_log.ol_timestamp) as latest
FROM orders
NATURAL JOIN orders_log
GROUP BY orders.*
) subquery
ON main.ol_timestamp = subquery.latest
AND main.o_id = subquery.o_id
This query is untested, but could you give it a try?
Then tell me the results.
NB - I am not sure if it is legal to use * on a GROUP BY clause, but if it
isnt please kindly substitute by orders.o_id, orders.next_field, etc...
Best,
Oliveiros
----- Original Message -----
From: "Gary Stainburn" <gary.stainburn@ringways.co.uk>
To: <pgsql-sql@postgresql.org>
Sent: Thursday, September 24, 2009 4:16 PM
Subject: [SQL] simple (?) join
> Hi folks.
>
> I have two tables
>
> create table orders (
> o_id serial primary key
> ...
> );
>
> create table orders_log (
> ol_id serial primary key,
> o_id int4 not null references orders(o_id),
> ol_timestamp timestamp,
> ol_user,
> );
>
> How can I select all from orders and the last (latest) entry from the
> orders_log?
>
> Cheers
> --
> Gary Stainburn
>
> Gary's Haircut 700
> Please visit http://www.justgiving.com/Gary-Stainburn/ to help me
> raise money for Cancer Research - in return I'll have my head shaved
>
>
> --
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