Catégories :: Fonctions géospatiales

ST_MAKEPOLYGON , ST_POLYGON¶

Constructs a GEOGRAPHY or GEOGRAPHY object that represents a polygon without holes. The function uses the specified LineString as the outer loop.

Voir aussi :: TO_GEOGRAPHY , TO_GEOMETRY

Syntaxe¶

ST_MAKEPOLYGON( <geography_or_geometry_expression> )

Arguments¶

geography_or_geometry_expression: A GEOGRAPHY or GEOMETRY object that represents a LineString in which the last point is the same as the first (i.e. a loop).

Renvoie¶

The function returns a value of type GEOGRAPHY or GEOMETRY.

Notes sur l’utilisation¶

The lines of the polygon must form a loop. Therefore, the last Point in the sequence of Points defining the LineString must be the same Point as the first Point in the sequence.
ST_POLYGON est un alias pour ST_MAKEPOLYGON.

For GEOMETRY objects, the returned GEOMETRY object has the same SRID as the input.

Exemples¶

GEOGRAPHY Examples¶

Cela montre une utilisation simple de la fonction ST_MAKEPOLYGON. La séquence de points ci-dessous définit une zone géodésique rectangulaire de 1 degré de large et de 2 degrés de haut, le coin inférieur gauche du polygone commençant à l’équateur (latitude) et à Greenwich (longitude). Le dernier point de la séquence est le même que le premier point, qui complète la boucle.

SELECT ST_MAKEPOLYGON(
   TO_GEOGRAPHY('LINESTRING(0.0 0.0, 1.0 0.0, 1.0 2.0, 0.0 2.0, 0.0 0.0)')
   ) AS polygon1;
+--------------------------------+
| POLYGON1                       |
|--------------------------------|
| POLYGON((0 0,1 0,1 2,0 2,0 0)) |
+--------------------------------+

GEOMETRY Examples¶

This shows a simple use of the ST_MAKEPOLYGON function.

SELECT ST_MAKEPOLYGON(
  TO_GEOMETRY('LINESTRING(0.0 0.0, 1.0 0.0, 1.0 2.0, 0.0 2.0, 0.0 0.0)')
  ) AS polygon;

+--------------------------------+
| POLYGON                        |
|--------------------------------|
| POLYGON((0 0,1 0,1 2,0 2,0 0)) |
+--------------------------------+