Hope this helps
SELECT*
FROMspeed_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
2005-08-1108:10:23 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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