ST_NumInteriorRings returns the number of rings in an input polygon geometry.
Syntax
ST_NumInteriorRings(geom)
Arguments
- geom
-
A value of data type
GEOMETRYor an expression that evaluates to aGEOMETRYtype.
Return type
INTEGER
If geom is null, then null is returned.
If geom is not a polygon, then null is returned.
Examples
The following SQL returns the number of interior rings in the input polygon.
SELECT ST_NumInteriorRings(ST_GeomFromText('POLYGON((0 0,100 0,100 100,0 100,0 0),(1 1,1 5,5 1,1 1),(7 7,7 8,8 7,7 7))'));
st_numinteriorrings
-------------
2
