[postgis-users] Merging Contour tables in PostGIS

[Paragon Corporation]

Max,
It looks like when you created your table you created ELEVATION as
"ELEVATION".   Better to not use quotes when defining fields since
PostgreSQL will take the column name literally rather than forcing to
lowercase.

Which means you have to refer to it as 

a."ELEVATION"

If you don't quote your columns during creation you can then refer to them
as

A.ELEVATION, a.elevation, a.Elevation etc. (in those cases it assumes the
field is lowercase and stores it as lowercase)

Leo

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Max Bott
Sent: Thursday, February 19, 2009 2:34 AM
To: postgis-users at postgis.refractions.net
Subject: [postgis-users] Merging Contour tables in PostGIS


Hi All,

I have 2 tables (contours1 & contours2) in my postgis database which I have
populated from shapefiles containing contours in adjacent geographic areas.
These 2 tables contain (amongst other things) the following columns

"ELEVATION" double precision,
the_geom geometry

To create my merged table covering the contours from both contours1 and
contours2 I used

SELECT a.ELEVATION,ST_LineMerge(ST_Collect(a.the_geom, b.the_geom)) AS
the_geom INTO merged_contours FROM
contours1 AS a,contours2 AS b
GROUP BY ELEVATION;

but that gave the result

********** Error **********

ERROR: column a.elevation does not exist SQL state: 42703
Character: 8

Any ideas?

Cheers,
Max

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