ST_MakePolygon-ApsaraDB RDS(RDS)-阿里云帮助中心

Constructs a polygon from one or more closed LineString geometries.

Syntax

geometry ST_MakePolygon(geometry linestring);
geometry ST_MakePolygon(geometry outerlinestring, geometry[] interiorlinestrings);

Parameters

Parameter	Description
`linestring`	A closed LineString that defines the outer shell of the polygon.
`outerlinestring`	A closed LineString that defines the outer shell.
`interiorlinestrings`	An array of closed LineStrings, each defining an inner shell (hole). Build the array using `ARRAY[]`.

Usage notes

Variant 1 accepts a single shell LineString and returns a simple polygon with no holes.

Variant 2 accepts an outer shell and an array of inner shells, and returns a polygon with one or more holes.

Both variants require a closed LineString — the first and last coordinates must be identical. Open LineStrings cause an error.

Examples

Variant 1: Single shell

Construct a simple polygon from a closed LineString.

SELECT ST_AsText(ST_MakePolygon(ST_GeomFromText('LINESTRING(1 2,3 4,5 6,1 2)')));

Output:

         st_astext
----------------------------
 POLYGON((1 2,3 4,5 6,1 2))
(1 row)

Variant 2: Outer shell with inner holes

Construct a polygon with one hole by passing an outer shell and an array containing one inner shell.

SELECT ST_AsText(
  ST_MakePolygon(
    ST_GeomFromText('LINESTRING(0 0,0 1,1 1,0 0)'),
    ARRAY[ST_GeomFromText('LINESTRING(-1 -1,-1 2,2 2,-1 -1)')]
  )
);

Output:

                     st_astext
---------------------------------------------------
 POLYGON((0 0,0 1,1 1,0 0),(-1 -1,-1 2,2 2,-1 -1))
(1 row)