ST_NUMGEOMETRIES

Description

Returns the number of sub-geometries contained in a geometry object. For non-collection types (Point, LineString, Polygon, Circle), it always returns 1. For collection types (MultiPolygon), it returns the number of sub-geometries in the collection.

Syntax

ST_NUMGEOMETRIES( <shape> )

Parameters

Parameter	Description
<shape>	The input geometry, of type GEOMETRY or VARCHAR (in WKT format) that can be converted to GEOMETRY.

Return Value

Returns a BIGINT value representing the number of sub-geometries in the geometry object.

ST_NUMGEOMETRIES has the following edge cases:

• If the input parameter is NULL, returns NULL.
• If the input parameter cannot be parsed into a valid geometry object, returns NULL.
• For non-collection types (POINT, LINESTRING, POLYGON, CIRCLE), always returns 1.
• For MULTIPOLYGON, returns the number of polygons in the collection.

Example

Number of geometries in a Point

SELECT ST_NUMGEOMETRIES(ST_Point(1, 2));

+----------------------------------+
| ST_NUMGEOMETRIES(ST_Point(1, 2)) |
+----------------------------------+
|                                1 |
+----------------------------------+

Number of geometries in a Polygon

SELECT ST_NUMGEOMETRIES(ST_GeometryFromText('POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))'));

+------------------------------------------------------------------------------+
| ST_NUMGEOMETRIES(ST_GeometryFromText('POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))')) |
+------------------------------------------------------------------------------+
|                                                                            1 |
+------------------------------------------------------------------------------+

Number of geometries in a MultiPolygon with two polygons

SELECT ST_NUMGEOMETRIES(ST_GeometryFromText('MULTIPOLYGON(((0 0, 1 0, 1 1, 0 1, 0 0)),((2 2, 3 2, 3 3, 2 3, 2 2)))'));

+------------------------------------------------------------------------------------------------------------------+
| ST_NUMGEOMETRIES(ST_GeometryFromText('MULTIPOLYGON(((0 0, 1 0, 1 1, 0 1, 0 0)),((2 2, 3 2, 3 3, 2 3, 2 2)))')) |
+------------------------------------------------------------------------------------------------------------------+
|                                                                                                                2 |
+------------------------------------------------------------------------------------------------------------------+

Number of geometries in a Circle

SELECT ST_NUMGEOMETRIES(ST_Circle(0, 0, 100));

+----------------------------------------+
| ST_NUMGEOMETRIES(ST_Circle(0, 0, 100)) |
+----------------------------------------+
|                                      1 |
+----------------------------------------+

NULL Parameter

SELECT ST_NUMGEOMETRIES(NULL);

+------------------------+
| ST_NUMGEOMETRIES(NULL) |
+------------------------+
|                   NULL |
+------------------------+

Invalid Parameter (Returns NULL)

SELECT ST_NUMGEOMETRIES(ST_GeometryFromText('INVALID'));

+--------------------------------------------------+
| ST_NUMGEOMETRIES(ST_GeometryFromText('INVALID')) |
+--------------------------------------------------+
|                                             NULL |
+--------------------------------------------------+