ST_EXTERIORRING()

All functions > GEOSPATIAL > ST_EXTERIORRING()

Returns the outer ring of a Polygon as a LineString.

Signatures

Exterior ring

Returns: Outer ring as a closed LineString

ST_EXTERIORRING(polygon: GEOM_POLYGON) → GEOM_LINESTRING

Signature notes:

• Input must be a Polygon; other sub kinds return NULL
• The returned LineString is closed (first vertex equals last vertex)
• GEOMETRY only; not supported on BigQuery
• Returns NULL if the input is NULL

Examples

SELECT
    f1 := ST_ASTEXT(ST_EXTERIORRING(ST_GEOMFROMTEXT('POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0))'))) -- Outer ring of a square polygon
;