[postgis-users] ST_Intersection

[jj.wag at gmx.de]

Nicolas,

> Is the select used to create the view returning rows ?
yes, I want to get the intersected parts of the polygonlayer and the area (I 
need the returned rows in a php application)

> Is this IsEmpty test necessary to validate there is an intersection ?
yes, because I want only the intersected rows

Jo


----- Original Message ----- 
From: "Nicolas Ribot" <nicolas.ribot at gmail.com>
To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
Sent: Friday, May 21, 2010 2:34 PM
Subject: Re: [postgis-users] ST_Intersection


>> Hi,
>>
>> I have a polygon table (alk_flurstuecke) and create a view with a 
>> 40-meter
>> buffer on an object:
>>
>> CREATE VIEW buffer_flur_40 AS
>> SELECT gid, ST_SetSRID(st_buffer(the_geom,40), 31466 )
>> AS the_geom FROM alk_flurstuecke WHERE fkz = '0726900330002300000';
>>
>> No problem, Ican see it in QGIS.
>> Now I try to make an intersection on this buffer-view with my table:
>>
>> CREATE VIEW intersect_flur_40 (gid, flur, zaehler, nenner, the_geom) AS
>> SELECT p.gid, p.flur, p.zaehler, p.nenner,
>> ST_SetSRID(ST_Intersection(p.the_geom, b.the_geom) ,31466)
>> AS the_geom FROM alk_flurstuecke AS p, buffer_flur_40 AS b
>> WHERE p.fkz <> '0726900330002300000' AND IsEmpty
>> (ST_Intersection(p.the_geom, b.the_geom) ) = FALSE;
>>
>> This view is created without errors too but there is no result. If I try 
>> to
>> load the view in QGIS it diapears.
>> Any idea?
>>
>
> Hi,
> Is the select used to create the view returning rows ?
> Is this IsEmpty test necessary to validate there is an intersection ?
>
> Nicolas
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