GeometryN(gc, N)

ST_GeometryN() and GeometryN() are synonyms. For more information, see the description of ST_GeometryN().

NumGeometries(gc)

ST_NumGeometries() and NumGeometries() are synonyms. For more information, see the description of ST_NumGeometries().

ST_GeometryN(gc, N)

Returns the N-th geometry in the GeometryCollection value gc. Geometries are numbered beginning with 1. If any argument is NULL or the geometry argument is an empty geometry, the return value is NULL.

mysql> SET @gc = 'GeometryCollection(Point(1 1),LineString(2 2, 3 3))';
mysql> SELECT ST_AsText(ST_GeometryN(ST_GeomFromText(@gc),1));
+-------------------------------------------------+
| ST_AsText(ST_GeometryN(ST_GeomFromText(@gc),1)) |
+-------------------------------------------------+
| POINT(1 1)                                      |
+-------------------------------------------------+

ST_GeometryN() and GeometryN() are synonyms.

ST_NumGeometries(gc)

Returns the number of geometries in the GeometryCollection value gc. If the argument is NULL or an empty geometry, the return value is NULL.

mysql> SET @gc = 'GeometryCollection(Point(1 1),LineString(2 2, 3 3))';
mysql> SELECT ST_NumGeometries(ST_GeomFromText(@gc));
+----------------------------------------+
| ST_NumGeometries(ST_GeomFromText(@gc)) |
+----------------------------------------+
|                                      2 |
+----------------------------------------+

ST_NumGeometries() and NumGeometries() are synonyms.