I'm making the transition from GIS to PostGIS and am stuck on this spatial query.
I have background geometry (purple, outlined red) which has an overlay of islands (blue, below); I need the area of only the islands within the red line. In GIS this would be a clip, using the purple shape as my mask.
And I can still find those islands overlapping the boundary of my polygon using ST_Overlap() to find these pink polygons:
But is there an efficient way to get the area of the islands only within the red outline? This will cut a percentage of the island polygons, I understand, those will be associated with the adjacent background polygon.