On 2025-09-30 16:08 +0200, celati Laurent wrote:
> I work with qgis and postgis. I would like to perform a "dissolve":
> https://docs.qgis.org/3.40/en/docs/user_manual/processing_algs/qgis/vectorgeometry.html#dissolve
>
> in keeping/preserving all attributes values ? For instance : a kind of
> aggregation/concatenation within new "output features" ?
>
> I Saw this post :
>
> https://www.aproposinfosystems.com/en/about/blog/managing-attributes-postgis-dissolve/
>
> I have tried to reproduce the proposal with my postgis table containing
> several polygons
>
> *SELECT min(union_v4.max_hierar) as id, array_agg(union_v4.id
> <http://union_v4.id>) as ids, union_v6.geomFROM union_v4, (SELECT
> (ST_Dump(St_multi(ST_Union(geom)))).geom as geom FROM union_v6WHERE
> st_intersects(union_v4.geom, union_v6.geom)GROUP BY union_v6.geom*
>
> But i obtain :
>
> *ERROR: syntax error at the end of the entryLINE 12: GROUP BY union_v6.geom
> ^ERROR: syntax error at the end of the entrySQL state: 42601Characters: 285*
Your query is missing the closing parenthesis of the union_v6 subquery
(after "FROM union_v6"). This should work:
SELECT
min(union_v4.max_hierar) as id,
array_agg(union_v4.id) as ids,
union_v6.geom
FROM union_v4,
(SELECT
(ST_Dump(St_multi(ST_Union(geom)))).geom as geom
FROM union_v6) union_v6
WHERE st_intersects(union_v4.geom, union_v6.geom)
GROUP BY union_v6.geom;
--
Erik Wienhold
