ST_INTERIORRINGN()

All functions > GEOSPATIAL > ST_INTERIORRINGN()

Returns the Nth interior ring (hole) of a Polygon as a LineString (1-indexed).

Signatures

Interior ring N

Returns: The Nth hole as a closed LineString

ST_INTERIORRINGN(polygon: GEOM_POLYGON, n: INT) → GEOM_LINESTRING

Signature notes:

• Index is 1-based
• Out of range index returns NULL
• Input must be a Polygon; other sub kinds return NULL
• GEOMETRY only; not supported on BigQuery
• Returns NULL if any input is NULL

Examples

SELECT
    -- First hole of a polygon with one hole
    f1 := ST_ASTEXT(
        ST_INTERIORRINGN(
            ST_GEOMFROMTEXT(
                'POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0), (2 2, 4 2, 4 4, 2 4, 2 2))'
            ),
            1
        )
    )
;