Touches(g1,g2)

Returns 1 or 0 to indicate whether g1 spatially touches g2. Two
geometries spatially touch if the interiors of the geometries do not
intersect, but the boundary of one of the geometries intersects either
the boundary or the interior of the other.

URL: http://dev.mysql.com/doc/refman/5.1/en/functions-that-test-spatial-relationships-between-geometries.html

