Tests if a geometry value spatially touches another geometry value.
Two geometries spatially touch if their interiors do not intersect but
one or more boundary points from one value intersects
the interior or boundary of the other value.
If the geometry-expression contains circular strings, then these are interpolated to line strings.
This method can not be used with geometries in round-Earth spatial reference system.
The following example returns NULL because both inputs are points and have no boundary.
SELECT NEW ST_Point(1,1).ST_Touches( NEW ST_Point( 1,1 ) )
The following example lists the ShapeIDs of the geometries that
touch the "Lighting Bolt" shape, which has ShapeID 6. This example
returns the result 5,16,26. Each of the three touching geometries intersect
the Lighting Bolt only at its boundary.
SELECT List( ShapeID ORDER BY ShapeID )
WHERE Shape.ST_Touches( ( SELECT Shape FROM SpatialShapes WHERE ShapeID = 6 ) ) = 1