[postgis-users] Examples SQL for spatial searches in post gis egintersect

[Abd Muhsen]

Hi,

I believe what Mr. Karim said is right. Using the && as an intersection 
operator is better since it allow the system to use the index (GiST, if 
available of course). I strongly recommend you to look at the following 
links. It might be very useful for you.

4.4. Retrieving GIS Data:
http://postgis.refractions.net/docs/ch04.html#id2849854

6.2.2. OpenGIS Operators:
http://postgis.refractions.net/docs/ch06.html#id2854381

Many thanks,

Abdel-Rahman Muhsen

MSc. Geomatics Engineering student
University of Calgary
Canada


>From: Maher Karim <Maher_Karim at dorsch.com.jo>
>Reply-To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
>To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
>CC: postgis-users 
><postgis-users at postgis.refractions.net>,postgis-users-bounces 
><postgis-users-bounces at postgis.refractions.net>
>Subject: Re: [postgis-users] Examples SQL for spatial searches in post gis 
>egintersect
>Date: Wed, 4 Apr 2007 07:14:37 +0200
>
>
>
>
>
>Hi Mohammed,
>
>You can use this example as a guide for you.
>select count(*) from layer1,layer2 where layer1.the_geom&&layer2.the_geom
>and intersects(layer1.the_geom,layer2.the_geom)
>
>you should use the "layer1.the_geom&&layer2.the_geom" because it will
>reduce the query time
>
>Regards
>Maher Abdel Karim
>GIS systems analyst/Programmer
>Dorsch Water and Environment
>
>
>
>|---------+--------------------------------------------->
>|         |           "Mohammed Wahead"                 |
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>post gis eg  intersect                                                      
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>
>
>Hi folks,
>
>
>Can anyone point mw in the right direction. I would like examples of SQL
>syntax for running spatial searches in postgis. For example what is the SQL
>for determining which spatial features intersect with another spatial
>feature.
>
>
>Thanks.
>
>
>Mohammed Wahead
>"Subscribe to Cadcorp eNews at www.cadcorp.com."
>
>GIS & RDBMS Specialist
>Cadcorp
>Computer Aided Development Corporation Ltd Sterling Court,
>Norton Road,
>Stevenage, Herts,
>SG1 2JY, UK
>Tel: +44 (0)1438 731440
>Fax: +44 (0)1438 747997
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