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In PostGIS 2.0, what is the most efficient way to create a spatially enabled view that is viewable in QGIS?

I followed the context of Part 2 of @Mike Toews answer to this question, and the view shows up as a point layer (in my case) in the "Add PostGIS Layers" dialog. But after creating the view and spatially enabling it, I received the following error when trying to add the view to QGIS:

You must select a table in order to add a layer

Can someone please explain why the spatial view will not load into QGIS, and what I need to do in order to make it loadable as a layer in QGIS?

UPDATE 1: (I'm currently using QGIS v1.8 from the OSGEO installer)

I view is built from the geonames database, loaded into PostGIS. The geoname table/spatial data can be selected/viewed in QGIS just fine.

When I try to select the "mt_view", QGIS sees the view in the dialog, but won't let me select it. It gives a dotted box around the area, but does not highlight and select the view.

QGIS cannot select the mt_view as a layer

UPDATE 2: I just noticed that when I run my first query:

SELECT * FROM data.geoname
WHERE admin1='MT'

the view shows up in the QGIS Add Layer Dialog, but is unselectable. Then when I run:

SELECT Populate_Geometry_Columns('data.test'::regclass);

I get the result of "0", where according to the documentation, I think it should be returning "1". Any thoughts?

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I confirm the problem. With QGIS 1.8, PostGIS 2.0, and a view created from a table with a primary key, tha view gets listed in the avaiable layers but the error message "You must select a table in order to add a layer" appears. –  giohappy Dec 3 '12 at 17:46
Is there another way to set automatically de primary key in Postgis Add Layer window when we work with views? It's very hard work to select a primary key field in this screen for any layers/views if you imagine a normal GIS user and a view have lots integer fields. –  user13835 Dec 28 '12 at 12:18
@Pgimenez, I would suggest starting a new question with what you stated above, and then reference this questions url in your own. That will give it much wider visibility. –  RyanDalton Dec 28 '12 at 18:24
There is no way to visualize a convexhull in qgis 1.8 lisboa? I have tried following vievs in Postgis 1.5 I Was told to use an id column to publish it in Qgis. If you not use an id column, u cannot load it anyway because of an error. 1. create or replace view con_hull_baeume3(bid) as select '0', ST_ConvexHull(ST_Collect(geom)) FROM baeume; 2. create or replace view con_hull_baeume4(bid) as select bid, ST_ConvexHull(ST_Collect(geom)) FROM baeume group by bid; but this one make a convexhull on each of the geometrypoints. I mean just use 'select ST_ConvexHull(ST_Collect(geom)) FROM baeume;' works –  ulan Mar 22 '13 at 8:53
Welcome! Please post this as a new question, since it doesn't seem to answer the original one. At least if it is a question, since the last statement isn't clear whether you succeeded or not. –  lynxlynxlynx Mar 22 '13 at 9:25

3 Answers 3

up vote 28 down vote accepted

I can confirm that it is not possible to simply select a listed view.

It seems necessary to select the "primary key column" first. Then the table turns selectable:

enter image description here

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Wow, I would have never seen that. Thanks so much! I've edited the title to reflect the issue was with QGIS, not the PostGIS view. –  RyanDalton May 18 '12 at 22:03
It appears this is an issue for QGIS 1.8 (which I haven't used yet). These steps are not required for 1.7. –  Mike T May 19 '12 at 21:54
That's right, 1.7 tried to guess the primary key. But it didn't work well. –  underdark Sep 3 '12 at 11:14
on a side note, @underdark, does QGIS accepts other types of PKs? –  George Nov 9 '12 at 15:49

Does your view show up in the geometry_columns table? According to the manual the view should automatically show up in 2.0 but I haven't tried it.

Try running the following to check:

SELECT f_geometry_column As col_name, type, srid, coord_dimension As ndims 
FROM geometry_columns
WHERE f_table_name = 'my_spatial_table' AND f_table_schema = 'my_schema';
share|improve this answer
Yes, running this check against my view does return: the_geom,Point,4269,2 –  RyanDalton May 18 '12 at 18:37

Is your view using an unique integer field like a "gid" or PK equivalent from one of the tables in your view?

I know that in previous versions of QGIS I have had problems with views being added to the map when there was no unique integer field. However I did receive a different error message pointing that issue out, but it may be worth checking to cover off all bases.

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Yes, the geonames table has "geonameid" that is a unique ID and has a PRIMARY KEY constraint set on that field. –  RyanDalton May 18 '12 at 18:41

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