MySQL:

ST_DIMENSION

ST_Dimension(g)

Returns the inherent dimension of the geometry value g. The dimension
can be ?1, 0, 1, or 2. The meaning of these values is given in
https://dev.mysql.com/doc/refman/8.0/en/gis-class-geometry.html.

ST_Dimension() handles its arguments as described in the introduction
to this section.

URL: https://dev.mysql.com/doc/refman/8.0/en/gis-general-property-functions.html

Example

mysql> SELECT ST_Dimension(ST_GeomFromText('LineString(1 1,2 2)'));
+------------------------------------------------------+
| ST_Dimension(ST_GeomFromText('LineString(1 1,2 2)')) |
+------------------------------------------------------+
| 1 |
+------------------------------------------------------+