Pulling additional columns with aggregate

From: sub3 <steve(at)subwest(dot)com>
To: pgsql-sql(at)postgresql(dot)org
Subject: Pulling additional columns with aggregate
Date: 2009-10-08 13:14:02
Message-ID: 25802979.post@talk.nabble.com
Views: Whole Thread | Raw Message | Download mbox | Resend email
Thread:
Lists: pgsql-sql


Hi,

I have 2 tables. I want to be able to calculate the closest value in one
(tempvalues), to the closest value in the other (points). This closest
point, I want to save into the table with its difference.

So if I have:

create table points (
id integer,
center double precision
);
insert into points values (1, 1),(2,4),(3,7),(4,12);

CREATE TABLE tempvalues (
id serial NOT NULL,
"value" double precision,
closest_point_id integer,
distance_to_point double precision,
CONSTRAINT tempvalues_pkey PRIMARY KEY (id),
CONSTRAINT tempvalues_closest_point_id_fkey FOREIGN KEY (closest_point_id)
REFERENCES points (id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE NO ACTION
);
insert into tempvalues (value) values
(1.1),(2.2),(3.3),(4.4),(5.5),(6.6),(7.7),(8.8),(9.9),
(10.1),(11.1),(12.2),(13.3),(14.4),(15.5),(16.6),(17.7),(18.8),(19.9),(20.0);

I would like to see each row in tempvalues populated with the closest point
from points and its difference.

I know I can find the cartesian product of the 2 tables, and get the
distance between all values.
select tempvalues.id as tid, points.id as pid,
min(abs(points.center-tempvalues.value))
from points, tempvalues group by tempvalues.id,points.id order by tid,pid

But I can't figure out how to return the result w/only 1 row per
tempvalue.id (the minimum) and still get the id column from each table. Any
aggregate with force those columns out.

I would love to do something like:
update tempvalues set closest_point_id,distance_to_point from (above
query)
but haven't been able to figure this out. Any suggestions?

Thanks.
--
View this message in context: http://www.nabble.com/Pulling-additional-columns-with-aggregate-tp25802979p25802979.html
Sent from the PostgreSQL - sql mailing list archive at Nabble.com.

Responses

Browse pgsql-sql by date

  From Date Subject
Next Message Lennin Caro 2009-10-08 14:44:48 Re: Pulling additional columns with aggregate
Previous Message Richard Huxton 2009-10-08 08:24:46 Re: Function Anomaly?