ST_Centroid function

The ST_Centroid function takes a geometry as an input parameter and returns the geometric center, which is the center of the minimum bounding rectangle of the specified geometry, as a point. The resulting point is represented in the spatial reference system of the specified geometry.

If the specified geometry is null or is empty, then null is returned.

Syntax

Parameter

geometry: A value of type ST_Geometry or one of its subtypes that represents the geometry to determine the geometric center.

Return type

ST_Point

Example

This example creates two geometries and finds the centroid of them.



CREATE TABLE sample_geoms (id INTEGER, geometry ST_Geometry)

INSERT INTO sample_geoms VALUES
    (1, ST_Polygon('polygon
    ((40 120, 90 120, 90 150, 40 150, 40 120),
    (50 130, 80 130, 80 140, 50 140, 50 130))',0))

INSERT INTO sample_geoms VALUES
    (2, ST_MultiPoint('multipoint(10 10, 50 10, 10 30)' ,0))


SELECT id, CAST(ST_AsText(ST_Centroid(geometry)) 
   as VARCHAR(40)) Centroid
FROM sample_geoms

Results:


ID          CENTROID
----------- ----------------------------------------
          1 POINT (65 135)
          2 POINT (30 20)