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Try use DB Manager (QGIS Plugin - Comes with standard installation
of QGIS), here you can connect to the database and run queries and
afterwards import the queries into QGIS.<br>
<br>
When you've create a link to your database in "Add PostGIS-layers"
(Ctrl + Shift + D) it should show up in DB manager :) Here it'll be
able to read the postgis-functions in the database.<br>
<br>
Hope it helps.<br>
<div class="moz-signature"><font face="Tahoma"> <br>
Mvh. / Best regards</font><br>
<div class="moz-signature"><font face="Tahoma"> </font><font
face="Tahoma">Casper Bertelsen</font><font face="Tahoma"><br>
<br>
Mail: <a class="moz-txt-link-abbreviated" href="mailto:casperbj94@gmail.com">casperbj94@gmail.com</a></font><br>
<div class="moz-signature"><font face="Tahoma"> <br>
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<div class="moz-cite-prefix">On 03-02-2018 14:06, image wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1517663172836-0.post@n6.nabble.com">
<pre wrap="">Good morning,
I have to do flow map (home->working place) for my area of interest (28
french cities).
I get a database .dbf created by a french institute. I imported it into
postgres/postgis.
One row = 1 people.
My table is composed by several fields :
id (primary key)
codgeo_res: residence (home) city 's id
x_resi: residence (home) city 's longitude(centroid)
y_resi : residence (home) city 's latitude(centroid)
codgeo_tr : work place city 's id
x_tr: work city 's longitude(centroid)
y_tr :work city 's latitude(centroid)
ipondi : poids de l'individu (weighting value assigned to each individual du
to the sampling)
geom : residence (home) city 's ponctual geometry (centroid)
So my goal is to create a new table in order 1 row = 1 flow (city A toward
city B)
I have to generate useful geometries (points + lines arrow). Moreover, have
to apply a SUM on the ipondi field and a GROUP BY on "codgeo_res" field.
Could you throw light for me? Could you help me in order to translate this
objective to functional sql queries?
Up to now, i tried to run this query throw qgis interface called "virtual
layer creation" :
------------------------------------------------------
Code:
select
st_makeline(st_makepoint(entrants_only.x_resi,entrants_only.y_resi),st_makepoint(entrants_only.x_tr,entrants_only.y_tr))as
geometry,sum(entrants_only.ipondi) as sumipondi, entrants_only.codgeo_res as
codgeo_res, entrants.codgeo_tr as codgeo_tr
from entrants_only
group by entrants_only.codgeo_res
--------------------------------------------------------
But i get this error message :
---------------------------------------------------------
query preparation error on PRAGMA table_info(_tview): no such column
entrants_only.geom
---------------------------------------------------------
Moreover, i send you by attachment the Screen shot representing the error
message.
<a class="moz-txt-link-rfc2396E" href="http://osgeo-org.1560.x6.nabble.com/file/t365144/ss_error_message_qgis2.jpg"><http://osgeo-org.1560.x6.nabble.com/file/t365144/ss_error_message_qgis2.jpg></a>
In advance, thank you for your help.
--
Sent from: <a class="moz-txt-link-freetext" href="http://osgeo-org.1560.x6.nabble.com/QGIS-User-f4125267.html">http://osgeo-org.1560.x6.nabble.com/QGIS-User-f4125267.html</a>
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