[postgis-users] sum or not sum..

[Michael Smedberg]

I think that your query is counting rows more than once, because you're doing a "Cartesian Product"; see http://www.dba-oracle.com/t_garmany_9_sql_cross_join.htm

 

I think you'd want to do something like:

 

select sum(area(a.the_geom)) as sum1,sum(area(b.the_geom))as sum2 from orig1 a,orig2  b where a.id = b.a_id

 

________________________________

From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Gustavo Ces
Sent: Thursday, February 07, 2008 7:35 AM
To: PostGIS Users Discussion
Subject: [postgis-users] sum or not sum..

 

Hi all,

 

    I´ve got two tables with geoms. When i try to sum(area) something strange happens:

 

select sum(area(the_geom)) from orig1

 

61301.4750045538


select sum(area(the_geom))from orig2

 

33996.0705435276

 

 

but now...

 

select sum(area(a.the_geom)) as sum1,sum(area(b.the_geom))as sum2 from orig1 a,orig2  b


sum1                        sum2

11218169.9258333     4963426.29935503

 

smells like postgresql basic concept unknowed for me.... :(

 

Gus

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