[postgis-users] Calculating Attributes

[George Silva]

Hello Aurora,

In ArcGIS it's all different. In PostGIS you can use simple/complex SQL
queries to "calculate values" in a similar fashion of arcgis.

The simplest of them all would be, in your case:

ALTER TABLE table1 ADD COLUMN area_column double precision;
UPDATE table1 SET area_column = ST_AREA(the_geom);

You can in that SQL query divide, multiply, and do whatever you want with
that result that will be written to the column area_column.

I hope that helps

George

On Fri, Apr 3, 2009 at 12:55 PM, Aurora Geomatics <aurorageomatics at gmail.com
> wrote:

> Hello PostGIS users,
>
> I have just installed William Kyng's PostgeSQ/PostGIS packages for Mac OS
> X.5
>
> I have been playing with pgAdmin and QGIS with importing shapefiles into
> PostGIS.  Works dandy.
>
> Now I am wondering how to solve Attribute Calculations.
>
> Years of using ArcGIS and GRASS it is pretty straightforward on those apps,
> and am stumped with PostGIS Attribute calculations..
>
> For example, using a polygon feature;
>
> Creating a new column, say AREA and filling with a calculation that is
> Hectares.
>
> Thanks!
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> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
>
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