The ST_BOUNDARY function was introduced in MariaDB 10.1.2
ST_BOUNDARY(g) BOUNDARY(g)
Returns a geometry that is the closure of the combinatorial boundary of the geometry value g
.
BOUNDARY() is a synonym.
SELECT ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(3 3,0 0, -3 3)'))); +----------------------------------------------------------------------+ | ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(3 3,0 0, -3 3)'))) | +----------------------------------------------------------------------+ | MULTIPOINT(3 3,-3 3) | +----------------------------------------------------------------------+ SELECT ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((3 3,0 0, -3 3, 3 3))'))); +--------------------------------------------------------------------------+ | ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((3 3,0 0, -3 3, 3 3))'))) | +--------------------------------------------------------------------------+ | LINESTRING(3 3,0 0,-3 3,3 3) | +--------------------------------------------------------------------------+
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https://mariadb.com/kb/en/boundary/