[postgis-users] sync geometry with attributes

[Obe, Regina]

John

There are two ways of dealing with this

1) Put in a trigger in your table so that when the geometry gets edited,
It updates your long = ST_X(the_geom)
	and your lat = ST_Y(the_geom)

2) The way I find easier to deal if you don't edit those fields directly
is just to get rid of your
long lat fields and create a view

CREATE VIEW vwmytable
AS 
	SELECT gid, field1, field2, field3, ST_X(the_geom) as long,
ST_Y(the_geom) As lat
	FROM mytable

 You can also put an update rule on your view so that if anyone tried to
edit the long, lat fields
then it will update the_geom field with something like

the_geom = CASE WHEN OLD.long <> NEW.long THEN ST_MakePoint(long, lat,
SRID(Old.the_geom)) ELSE NEW.the_geom END

Hope that helps,
R

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of John
Callahan
Sent: Friday, May 23, 2008 3:49 PM
To: postgis-users at postgis.refractions.net
Subject: [postgis-users] sync geometry with attributes

Please excuse my question if it seems too trivial.  I am just getting 
started with PostGIS and couldn't quite find what I was looking for.

For a point data set, it is common for us to store the lat/long (or 
easting/northing) as attributes in the table. (Some programs we have 
require this.)  However, when I edit the position through a GIS (like 
QGIS), the spatial location is altered but obviously not the 
attributes.  And when these attributes are altered in the table, the 
geometry is not updated, obviously.   Is there a way to keep these 
synchronized?  Is this built into PostGIS? 

Thanks for your help.  Even is you don't know how this could be done, is

it possible?

- John

****************************************
John Callahan
Geospatial Application Developer

Delaware Geological Survey
University of Delaware
227 Academy St, Newark DE 19716-7501
Tel: (302) 831-3584  

Email: john.callahan at udel.edu
http://www.dgs.udel.edu
****************************************

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