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

Builds an areal geometry from the constituent lines of the input geometry.

Syntax

geometry ST_BuildArea(geometry a);

Parameter	Description
`a`	The input geometry. Supported types: LineString, MultiLineString, Polygon, MultiPolygon, and GeometryCollection.

ST_BuildArea attempts to form a polygon or MultiPolygon from the lines that make up the input geometry. All inner geometries are treated as holes.

The function returns a polygon or MultiPolygon. Returns null if the constituent lines cannot form a closed polygon.

Build a polygon from a MultiLineString:

SELECT ST_AsText(ST_BuildArea('MultiLineString((0 0,0 1),(0 1,1 1),(1 1,0 0))'::geometry));

Output:

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