2

I need to know which points from Table 1 are contained in Table 2.

In Table 1 I have longitude and latitude and I made points with ST_SetSRID(ST_MakePoint(d.longitude, d.latitude),4326) as geom

Table 2 has a collection of multipolygons: geom geometry(MultiPolygon,4326)

I know it is a collection because when I run select ST_IsCollection(geom)from table2 it is TRUE, but when I want to know how many collections with SELECT ST_NumGeometries(geom)from table 2, it returns 1.

I know that since I have a collection I have to use st_INTERSECTS.

select TABLE1.*, TABLE2.*
from TABLE1, TABLE2
where ST_Intersects(TABLE2.geom, TABLE1.geom)

But it is empty. And I know from plotting the data that they intersect.

Do you know what might be wrong?

  • 3
    you are missing aliases, e.g. TABLE1 AS T1, TABLE2 AS T2 – Taras Apr 11 at 13:24
  • Yes @BERA is postgis – Florencia Diaz Apr 11 at 13:29
  • 2
    you're title is misleading -- its a multipolygon collection. If I were you I would dump the collection into an actual geometry. I think postgis recently allowed collections to be used in spatial functions such as st_intersects but that depends on what version of postgis you have – ziggy Apr 11 at 14:12
3

Have a look at St_Dump: https://postgis.net/docs/ST_Dump.html and Using multipolygon or polygon features for large intersect operations?

Assuming that Table2 are the polygons, this would be:

select T1.*, T2.*
from TABLE1 as T1, TABLE2 as T2
where ST_Intersects(St_Dump(T2.geom), T1.geom)
  • No Pieter, thanks, but that is not the problem. I edited the question, I wrote T1 T2 for convenience. – Florencia Diaz Apr 11 at 13:40

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