ST_NDims returns the coordinate dimension of a geometry. ST_NDims doesn't consider the topological dimension of a geometry. Instead, it returns a constant value depending on the dimension of the geometry.
Syntax
ST_NDims(geom)
Arguments
- geom
-
A value of data type
GEOMETRYor an expression that evaluates to aGEOMETRYtype.
Return type
INTEGER representing the inherent dimension of geom.
If geom is null, then null is returned.
The values returned are as follows.
| Returned value | Dimension of input geometry |
|---|---|
2 |
2D |
3 |
3DZ or 3DM |
4 |
4D |
Examples
The following SQL returns the number of dimensions of a 2D linestring.
SELECT ST_NDims(ST_GeomFromText('LINESTRING(0 0,1 1,2 2,0 0)'));
st_ndims
-------------
2
The following SQL returns the number of dimensions of a 3DZ linestring.
SELECT ST_NDims(ST_GeomFromText('LINESTRING Z(0 0 3,1 1 3,2 2 3,0 0 3)'));
st_ndims
-------------
3
The following SQL returns the number of dimensions of a 3DM linestring.
SELECT ST_NDims(ST_GeomFromText('LINESTRING M(0 0 4,1 1 4,2 2 4,0 0 4)'));
st_ndims
-------------
3
The following SQL returns the number of dimensions of a 4D linestring.
SELECT ST_NDims(ST_GeomFromText('LINESTRING ZM(0 0 3 4,1 1 3 4,2 2 3 4,0 0 3 4)'));
st_ndims
-------------
4
