14.16.5 MySQL-Specific Functions That Create Geometry Values

MySQL provides a set of useful nonstandard functions for creating geometry values. The functions described in this section are MySQL extensions to the OpenGIS specification.

These functions produce geometry objects from either WKB values or geometry objects as arguments. If any argument is not a proper WKB or geometry representation of the proper object type, the return value is NULL.

For example, you can insert the geometry return value from Point() directly into a POINT column:

INSERT INTO t1 (pt_col) VALUES(Point(1,2));

• GeomCollection(g [, g] ...)

  Constructs a GeomCollection value from the geometry arguments.

  GeomCollection() returns all the proper geometries contained in the arguments even if a nonsupported geometry is present.

  GeomCollection() with no arguments is permitted as a way to create an empty geometry. Also, functions such as ST_GeomFromText() that accept WKT geometry collection arguments understand both OpenGIS 'GEOMETRYCOLLECTION EMPTY' standard syntax and MySQL 'GEOMETRYCOLLECTION()' nonstandard syntax.

  GeomCollection() and GeometryCollection() are synonymous, with GeomCollection() the preferred function.

• GeometryCollection(g [, g] ...)

  Constructs a GeomCollection value from the geometry arguments.

  GeometryCollection() returns all the proper geometries contained in the arguments even if a nonsupported geometry is present.

  GeometryCollection() with no arguments is permitted as a way to create an empty geometry. Also, functions such as ST_GeomFromText() that accept WKT geometry collection arguments understand both OpenGIS 'GEOMETRYCOLLECTION EMPTY' standard syntax and MySQL 'GEOMETRYCOLLECTION()' nonstandard syntax.

  GeomCollection() and GeometryCollection() are synonymous, with GeomCollection() the preferred function.

• LineString(pt [, pt] ...)

  Constructs a LineString value from a number of Point or WKB Point arguments. If the number of arguments is less than two, the return value is NULL.

• MultiLineString(ls [, ls] ...)

  Constructs a MultiLineString value using LineString or WKB LineString arguments.

• MultiPoint(pt [, pt2] ...)

  Constructs a MultiPoint value using Point or WKB Point arguments.

• MultiPolygon(poly [, poly] ...)

  Constructs a MultiPolygon value from a set of Polygon or WKB Polygon arguments.

• Point(x, y)

  Constructs a Point using its coordinates.

• Polygon(ls [, ls] ...)

  Constructs a Polygon value from a number of LineString or WKB LineString arguments. If any argument does not represent a LinearRing (that is, not a closed and simple LineString), the return value is NULL.