[Qgis-user] Spatialite VIEW in QGIS question

Thu Feb 20 19:11:14 PST 2014

>
> Hi Olivier,
> thank you for trying to help,
> but, ermm, actually I do not see the point performing this. I have not
> really a problem creating views, but more making these functional in QGIS.
> Your example, as far as i understand, lacks a join-part completely, but
> thats the culprit I fear.

OK I misunderstood your problem, I though you had trouble loading the view,
which is not that straightforward...

As Bo Victor said, your view has the problem that it does not have unique
IDs which are necessary to have working spatial views.

But still, it seems your doing something wrong : if the idea is to have all
of the observations as an attribute for each polygon, you must return each
polygon in only one row, and aggregate the related data in that row. If you
don't, you'll end up with duplicated polygons like Bo Victor said, which
will probably be quite unusable...

Maybe you rather need a view looking like :

CREATE VIEW "Testview23" AS
SELECT "a"."ROWID" AS "ROWID", "a"."Geometry" AS "Geometry",
GROUP_CONCAT("b"."ora_nachweis_id") AS "ora_nachweis_id",
GROUP_CONCAT("b"."zahl") AS "zahl",
GROUP_CONCAT("b"."jahr") AS "jahr",
GROUP_CONCAT("b"."art") AS "art",
GROUP_CONCAT("b"."sta") AS "sta"
FROM "ASK_VOEGEL" AS "a"
JOIN "ask_art" AS "b" USING ("id")
GROUP BY a.ROWID

This way you'll get all of the species (comma separated) as attribute of
the polygon.

Hope it helps this time...

Olivier

2014-02-20 19:34 GMT+01:00 Bernd Vogelgesang <bernd.vogelgesang at gmx.de>:

>  Am 20.02.2014 18:13, schrieb Olivier Dalang:
>
> Bernd,
>
> Here's a procedure which works here on QGIS master :
>
> 1. Create a spatialite layer "countries" with fields "name" and a geometry
> column "geom" of type polygon.
>
> 2. Add some features to that layer.
>
> 3. In the DB manager, create the view:
> CREATE VIEW countries_influence AS
> SELECT rowid as rowid, name, Buffer(geom,1) as geom FROM countries
>
> 4. In the DB manager, register the view:
> INSERT INTO views_geometry_columns VALUES
> ('countries_influence','geom','rowid','countries','geom',1)
>
> 5. Reload the database in the DB manager and right-click : "add to the
> canvas".... It does NOT work.
>
> 6. From the "layer" menu, choose "add a spatialite layer", navigate to
> your db, choose the view, and, tadaaam, it WORKS !
>
> Let me know if it works...
> It seems the bugs comes from that "add to the canvas" function, which sets
> the source to
>
> path/SpatialiteView.sqlite' table="countries_influence" () sql=
>  instead of
> path/SpatialiteView.sqlite' table="countries_influence" (geom) sql=
>
> Regards,
>
>  Olivier
>
>
> Hi Olivier,
> thank you for trying to help,
> but, ermm, actually I do not see the point performing this. I have not
> really a problem creating views, but more making these functional in QGIS.
> Your example, as far as i understand, lacks a join-part completely, but
> thats the culprit I fear.
>
> I uploaded my testdb to dropbox.
> https://www.dropbox.com/s/8b1g97qu3us15tq/asktest3.sqlite
>
> There is only layer, a view and the table.
>
> Could anyone try it out?
> When you query the view with SELECT * FROM "Testview22" , I see the list
> of observation I would like also to see in the QGIS attribute table, but
> this just doesn't work. It also show 746 rows, but only 37 distinct sets of
> information.
>
> Cheers
> Bernd
>
>
>
>
> 2014-02-20 16:51 GMT+01:00 Bernd Vogelgesang <bernd.vogelgesang at gmx.de>:
> >
> > Am 19.02.2014 20:02, schrieb Olivier Dalang:
> >
> > Dear Bernd,
> >
> > I encountered some similar problems with Spatialite views, but in the
> end I had it working (sometimes) both in 2.0 and in master... I used the
> manual method from the spatialite cookbook though (not the Spatialite GUI).
> >
> > I have no time to test now, but from what I recall, this does not work :
> > CREATE VIEW AS SELECT name, geometry FROM table
> > while this works :
> > CREATE VIEW AS SELECT ROWID, name, geometry FROM table
> >
> > Maybe you want to give it a last try. I can testify I have some working
> spatialite views here. Let us know if this works, if not I may give it a
> better look when I have some time.
> >
> > Another method is running a SELECT query in the DB Manager in QGIS, and
> then choosing "Add to map canvas". This is not an actual sqlite view, but
> depending on what you need, it could be enough.
> >
> >
> > Hi Olivier,
> > added ROWID to the VIEW. Same result in QGIS.
> >
> > I also performed the select in the DB Manager as you proposed. When
> executed, it perfectly show the results i would like to see in the
> attribute table, but what "arrives" in the attribute table after loading as
> layer is again the duplication of the the first entry for ROWID of the
> polygon.
> >
> > So, this is my select: Anything important missing?
> >
> > SELECT "a"."ROWID" AS "ROWID", "a"."Geometry" AS "Geometry",
> >     "b"."zahl" AS "zahl", "b"."jahr" AS "jahr", "b"."art" AS "art",
> >     "b"."sta" AS "sta"
> > FROM "ASK_VOEGEL" AS "a"
> > JOIN "ask_art" AS "b" USING ("id")
> >
> >
> > Thanx for your time
> > Bernd
> >
> >
> > Good luck !
> >
> > Olivier
> >
> >
> >
> >
> >
> > 2014-02-19 19:54 GMT+01:00 Bernd Vogelgesang <bernd.vogelgesang at gmx.de>:
> >>
> >> Am 19.02.2014 19:14, schrieb Steve G:
> >>
> >>> This does not directly answer your question about spatialite views,
> but you
> >>> might be able to use relationships directly in QGIS in the near future
> (I
> >>> think this is a 2.1 update).  See:
> >>>
> >>> http://blog.vitu.ch/10112013-1201/qgis-relations
> >>>
> >>>
> >>> -Steve
> >>
> >>
> >> Hi Steve,
> >> Actually I do not care by which means I reach my destination, but I had
> the, maybe wrong; impression that using a spatial database would do the
> trick.
> >> Anyway ...
> >> I already installed latest master cause I read about this relation
> manager thing a while ago ... but I was left quite clueless about how to
> use it.
> >> Searched the web for nearly an hour about any info but to no avail, so
> many thanks for sharing the link!!
> >>
> >> Will have a look at it ASAP, maybe thats kind of a solution.
> >>
> >> Cheers
> >> Bernd
> >>
> >>
> >>
> >>> --
> >>> View this message in context:
> http://osgeo-org.1560.x6.nabble.com/Spatialite-VIEW-in-QGIS-question-tp5104565p5104775.html
> >>> Sent from the Quantum GIS - User mailing list archive at Nabble.com.
> >>> _______________________________________________
> >>> Qgis-user mailing list
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> >>> http://lists.osgeo.org/mailman/listinfo/qgis-user
> >>
> >>
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> >
> >
> >
>
>
>
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