Intersecting geometries

In PostGIS, there are two ways in which geometries can be intersected. The first way is checking whether two geometries intersect (at least one point of geometry A lies within the interior of geometry B). That's the ST_Intersects function. It accepts two arguments of the geometry type, and returns a Boolean.

For example, these lines intersect:

  SELECT ST_Intersects(
    ST_MakeLine(ST_MakePoint(20,50),ST_MakePoint(21,51)),
    ST_MakeLine(ST_MakePoint(20.5,50.5), ST_MakePoint(22,52))
);

But these lines don't:

     st_intersects
---------------
 t

SELECT ST_Intersects(
    ST_MakeLine(ST_MakePoint(20,50),ST_MakePoint(21,51)),
    ST_MakeLine(ST_MakePoint(21.5,51.5), ST_MakePoint(22,52))
);

 st_intersects
---------------
 f 

ST_Intersects can also be used for table joining. The following query will return land features that had at least one earthquake:

SELECT ne_110m_land.* FROM data_import...