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

Returns the inherent dimension of a geometry object.

Syntax

integer ST_Dimension(geometry g);

Parameter	Description
`g`	The geometry object.

The return value depends on the type of the input geometry object.

Input type	Return value
Point	`0`
LineString	`1`
Polygon	`2`
GeometryCollection	The largest dimension among all components in the collection.
Empty GeometryCollection (or any geometry with unknown dimension)	`0`

ST_Dimension also supports polyhedral surfaces, triangles, Triangulated Irregular Network (TIN) surfaces, and 3D objects.

Point

SELECT ST_Dimension('POINT(1 0)');
 st_dimension
--------------
            0
(1 row)

GeometryCollection containing a LineString and a Point

The function returns 1 because LineString has the largest dimension among the components.

SELECT ST_Dimension('GEOMETRYCOLLECTION(LINESTRING(0 0,1 0),POINT(1 0))');
 st_dimension
--------------
            1
(1 row)