ST_AsGeoJSON(g [, max_dec_digits [, options]])

Generates a GeoJSON object from the geometry g. The object string has
the connection character set and collation.

If any argument is NULL, the return value is NULL. If any non-NULL
argument is invalid, an error occurs.

URL: https://dev.mysql.com/doc/refman/8.0/en/spatial-geojson-functions.html

