ST_Difference(g1, g2)

Returns a geometry that represents the point set difference of the
geometry values g1 and g2. The result is in the same SRS as the
geometry arguments.

ST_Difference() permits arguments in either a Cartesian or a geographic
SRS, and handles its arguments as described in the introduction to this
section.

URL: https://dev.mysql.com/doc/refman/8.4/en/spatial-operator-functions.html

