[postgis-users] Calculating Attributes

[Aurora Geomatics]

Thank you George,

On 3-Apr-09, at 9:22 AM, George Silva wrote:

> 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.
>

Pretty straight forward SQL statement.
Is this a matter of opening a Terminal session using psql monitor?

Is it possible through pgAdmin or QGIS?

Thanks.

> 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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