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ST_NumGeometries

Returns the number of geometries in a geometry collection or Multi* geometry.

Syntax​

ST_NumGeometries(geometry)

Parameters​

ParameterTypeDescription
geometryGeometryInput geometry

Returns​

TypeDescription
Int64Number of component geometries

Examples​

Count in MultiPolygon​

SELECT ST_NumGeometries(ST_GeomFromText(
    'MULTIPOLYGON(((0 0, 1 0, 1 1, 0 1, 0 0)), ((2 2, 3 2, 3 3, 2 3, 2 2)))'
));
-- Returns: 2

Count in GeometryCollection​

SELECT ST_NumGeometries(ST_GeomFromText(
    'GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(1 1, 2 2), POLYGON((3 3, 4 3, 4 4, 3 4, 3 3)))'
));
-- Returns: 3

Single Geometry​

SELECT ST_NumGeometries(ST_GeomFromText('POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))'));
-- Returns: 1

Find Multi-Part Features​

SELECT id, ST_NumGeometries(geom) as part_count
FROM parcels
WHERE ST_NumGeometries(geom) > 1;

Notes​

  • Single geometries (Point, LineString, Polygon) return 1
  • Multi* geometries return count of components
  • GeometryCollections return count of contained geometries
  • Useful for identifying multi-part features

See Also​