In the section Geometry property functions, we've already discussed some functions that can construct new geometries from the existing ones:
Envelope(g)
StartPoint(ls)
EndPoint(ls)
PointN(ls,n)
ExteriorRing(poly)
InteriorRingN(poly,n)
GeometryN(gc,n)
OpenGIS proposes a number of other functions that can produce geometries. They are designed to implement Spatial Operators.
These functions are not yet implemented in MySQL. They should appear in future releases.
Intersection(g1,g2) | Returns a geometry that represents the point set intersection of the geometry values g1 with g2. |
Union(g1,g2) | Returns a geometry that represents the point set union of the geometry values g1 and g2. |
Difference(g1,g2) | Returns a geometry that represents the point set difference of the geometry value g1 with g2. |
SymDifference(g1,g2) | Returns a geometry that represents the point set symmetric difference of the geometry value g1 with g2. |
Buffer(g,d) | Returns a geometry that represents all points whose distance from the geometry value g is less than or equal to a distance of d. |
ConvexHull(g) | Returns a geometry that represents the convex hull of the geometry value g. |