Syntax
------ 
ST_Centroid(mpoly)
Centroid(mpoly)
 
Description
----------- 
Returns a point reflecting the mathematical centroid
(geometric center) for the MultiPolygon mpoly. The resulting
point will not necessarily be on the MultiPolygon. 
 
ST_Centroid() and Centroid() are synonyms.
 
Examples
-------- 
SET @poly = ST_GeomFromText('POLYGON((0 0,20 0,20 20,0 20,0
0))');
SELECT ST_AsText(ST_Centroid(@poly)) AS center;
 
+--------------+
| center |
+--------------+
| POINT(10 10) |
+--------------+
 

 
 
 
 
 
 
 

URL: https://mariadb.com/kb/en/st_centroid/