From: Nick Stone <nick@harelane.com>
To: 'Lane Van Ingen' <lvaningen@esncc.com>
To: pgsql-sql@postgresql.org
Subject: Re: SQL Newbie
Date: Fri, 12 Aug 2005 18:57:34 +0100
Message-ID: <20050812175529.82D7F24F3B9@smtp.nildram.co.uk> (raw)
In-Reply-To: <EKEMKEFLOMKDDLIALABIKEEECBAA.lvaningen@esncc.com>
Hope this helps
SELECT
*
FROM
speed_history as outside etc..
WHERE
(speed = (
SELECT
speed
FROM
speed_history as inside etc..
WHERE
(outside.interface = inside.interface)
LIMIT 1
ORDER BY
speed DESC
)
)
Hopefully you get the idea - basically it's a corelated sub-query - very
useful
Nick
-----Original Message-----
From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org]
On Behalf Of Lane Van Ingen
Sent: 12 August 2005 16:09
To: pgsql-sql@postgresql.org
Subject: [SQL] SQL Newbie
It seems to me that I should be able to do this, but after 5 hrs of trying,
I can't figure this one out.
I could do this in two queries, but seems like I should be able to do this
in one. What I am trying to do:
Find the highest speed at which each interface of a router has run over
time.
I have three tables, two of which (interface, speed_history) are being used
in this query (primary / foreign key fields noted as PK / FK):
router -> 1:M -> interface -> 1:M -> speed_history
------------------- --------------------------- --------------------------
-
router_no (int2) PK interface_id (int4) PK interface_id (int4) PK
name (varchar) router_no (int2) FK updated_time (timestamp)
PK
link_description (varchar) speed (int4)
Data in speed history looks like this:
interface_id updated_time speed
1 2005-08-11 08:10:23 450112
1 2005-08-11 10:53:34 501120 <---
1 2005-08-11 10:58:11 450112
2 2005-08-11 08:10:23 450112 <---
2 2005-08-11 11:00:44 350234
3 2005-08-11 08:10:23 450112 <---
The rows of speed_history I want back are marked above with ' <--- '.
Query results should look like:
interface.interface_id
interface.link_description
speed_history.updated_time
speed_history.speed
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To: pgsql-sql@postgresql.org
Cc: nick@harelane.com, lvaningen@esncc.com
Subject: Re: SQL Newbie
In-Reply-To: <20050812175529.82D7F24F3B9@smtp.nildram.co.uk>
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