Hi Tasneem,
You will have to create a geometry first before you can use postgis
functions. Just 2 columns with coordinates are not enough (you're very
close though).
I would recommend to do some reading in the manual, especially here:
http://postgis.refractions.net/documentation/manual-2.0/PostGIS_FAQ.html#id605751
It boils down to adding a column with
SELECT AddGeometryColumn('', 'yourtable','geom',-1,'POINT',2);
and then filling the column with
UPDATE yourtable SET geom = ST_SetSrid(ST_MakePoint(xcolumn,
ycolumn),4326)
(see:
http://postgis.refractions.net/documentation/manual-2.0/ST_MakePoint.html)
Besides that: most likely you want to use ST_DWithin, it's supposed to
be faster than ST_Within.
Cheers,
Tom
On 8-10-2012 14:40, tasneem dewaswala wrote:
Hello,
I am developing an application to find whether two cars are in each
other communication range or not.
I have two tables like receiver and transmitter. i would like to know
if receiver is in 100 meters range of transmitter or not.
Since i am using PostgreSQL first time, i donno much about its
functions and commands, but i have found that there is ST_Within(),
which can be used for my work. I tried but it gives me lot of errors,
probably because of data types of my latitude and longitude. they are
in two different columns with datatype as double precision.
please tell me what is wrong, and how should i use ST_WITHIN for my
work. Or tell me any other way of knowing if two objects are in range
of each other.
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