[postgis-users] geometry type issue

[Bo Victor Thomsen]

(not tested !!)

UPDATE a_table AS a SET a.geom = b.cgeom from (select name, 
ST_ConcaveHull(ST_Collect(geom), 0.99) as cgeom from b_table group by 
name having count(*) >= 3) AS b WHERE a.name = b.name

the "count(*) >= 3" removes point collections which will result in 
degenerative concave hulls


Den 27-04-2020 kl. 12:29 skrev Shaozhong SHI:
> I added a new column.
>
> alter table a_table add column geom geometry(Polygon, 27700);
>
> Then,
>
> update a_table set geom = (select ST_ConcaveHull(ST_Collect(geom), 
> 0.99) from b_table where name = _name) where name = _name;
>
> It kept throwing up an error message saying: "geometry type point does 
> not match polygon".
>
> I thought that a concavehyll is a polygon.  That is why I created a 
> polygon column for it.
>
> Can anyone help?
>
> Regards,
>
> Shao
>
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-- 
Med venlig hilsen / Kind regards

Bo Victor Thomsen

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