st_nrings function

Applies to: Databricks SQL Databricks Runtime 18.1 and above

Returns the total number of rings of the input polygon or multipolygon, including exterior and interior rings. For a multipolygon, returns the sum of all rings across all polygons.

Syntax

st_nrings ( geoExpr )

Arguments

• geoExpr: A GEOGRAPHY or GEOMETRY value.

Returns

An INTEGER value that represents the total number of rings in the input polygon or multipolygon.

Notes

The function returns NULL if the input is NULL.

Error conditions

• If geoExpr is not a polygon or multipolygon, the function returns ST_INVALID_ARGUMENT.INVALID_TYPE.

Examples

-- Example taking an empty 2D polygon GEOMETRY.
> SELECT st_nrings(st_geomfromtext('POLYGON EMPTY'));
  0
-- Example taking a 4D polygon GEOGRAPHY with two rings (one exterior, one interior).
> SELECT st_nrings(st_geogfromtext('POLYGON ZM ((0 0 111 -11,10 0 222 -22,0 10 333 -33,0 0 444 -44),(1 1 555 -55,4 1 666 -66,1 4 777 -77,1 1 888 -88))'));
  2
-- Example taking an empty 3DZ multipolygon GEOMETRY.
> SELECT st_nrings(st_geomfromtext('MULTIPOLYGON Z EMPTY', 4326));
  0
-- Example taking a multipolygon GEOGRAPHY with four rings across two polygons.
> SELECT st_nrings(st_geogfromtext('MULTIPOLYGON (((0 0,10 0,10 10,0 10,0 0),(1 1,4 1,4 4,1 4,1 1),(5 5,6 5,6 6,5 6,5 5)),((20 20,30 20,30 30,20 30,20 20)))'));
  4

Related functions

• st_exteriorring function
• st_interiorringn function
• st_numinteriorrings function
• st_makepolygon function