PostGIS intersect two polygons from geom tables PostgreSQL

Question

I want to intersect two polygons; they are in two tables stored in PostgreSQL. The names are "poligono" and "categorias_eot_paramo", respectively.

I am using the next simple syntax because I want to check the results where polígono intersect categorias_eot_paramo with the attributes from table categorias_eot_paramo.

SELECT ST_AsText(ST_Intersection(poligono.geom, categorias_eot_paramo)); 

and then, I got the next error:

ERROR:  missing FROM-clause entry for table "poligono"
LINE 1: SELECT ST_AsText(ST_Intersection(poligono.geom, categorias_e...
                                         ^
SQL state: 42P01
Character: 34

Answer 1

As the error message says, you must specify the involved tables in the from clause. You may also want to limit the result to the actual intersections, else it would also create empty intersections.

SELECT ST_AsText(ST_Intersection(poligono.geom, categorias_eot_paramo.geom))
FROM poligono
 JOIN categorias_eot_paramo
  ON ST_INTERSECTS(poligono.geom, categorias_eot_paramo.geom);