Geometry Property Functions • ST_StartPoint( ls ) •If any argument is  NULL  or any geometry argument is an empty geometry, the return value is  NULL . •If any geometry argument is not a syntactically well-formed geometry, an  ER_GIS_INVALID_DATA  error occurs. •If any geometry argument is a syntactically well-formed geometry in an undefined spatial reference system (SRS), an  ER_SRS_NOT_FOUND  error occurs. •For functions that take multiple geometry arguments, if those arguments are not in the same SRS, an ER_GIS_DIFFERENT_SRIDS  error occurs. •Otherwise, the return value is non- NULL . • ST_Area({ poly | mpoly }) •If the geometry is geometrically invalid, either the result is an undefined area (that is, it can be any number), or an error occurs. •If the geometry is valid but is not a  Polygon  or  MultiPolygon  object, an ER_UNEXPECTED_GEOMETRY_TYPE  error occurs. •If the geometry is a valid  Polygon  in a Cartesian SRS, the result is the Cartesian area of the polygon. •If the geometry is a valid  MultiPolygon  in a Cartesian SRS, the result is the sum of the Cartesian area of the polygons. •If the geometry is a valid  Polygon  in a geographic SRS, the result is the geodetic area of the polygon in that SRS, in square meters. •If the geometry is a valid  MultiPolygon  in a geographic SRS, the result is the sum of geodetic area of the polygons in that SRS, in square meters. 2313 As of MySQL 8.0.13,  ST_Area()  handles its arguments as described in the introduction to this section, with these exceptions: Returns a double-precision number indicating the area of the  Polygon  or  MultiPolygon  argument, as measured in its spatial reference system. These functions are available for obtaining polygon properties: Unless otherwise specified, functions in this section handle their geometry arguments as follows: Functions in this section return properties of  Polygon  or  MultiPolygon  values. Returns the  Point  that is the start point of the  LineString  value  ls . ST_StartPoint()  handles its arguments as described in the introduction to this section. mysql>  SET @ls = ’LineString(1 1,2 2,3 3)’; mysql>  SELECT ST_AsText(ST_StartPoint(ST_GeomFromText(@ls))); +------------------------------------------------+ | ST_AsText(ST_StartPoint(ST_GeomFromText(@ls))) | +------------------------------------------------+ | POINT(1 1) | +------------------------------------------------+ 12.17.7.4 Polygon and MultiPolygon Property Functions