MySQL 8.0

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select version();

version()

8.0.23

SET @pt1 = ST_GeomFromText('POINT(0 0)');
SET @pt2 = ST_GeomFromText('POINT(0 1)');
SELECT ST_Distance_Sphere(@pt1, @pt1, 0);
show warnings

Level
Code
Message

Error
3706
Invalid radius provided to function st_distance_sphere: Radius must be greater than zero.

SELECT ST_Distance_Sphere(@pt1, @pt2, 1);

ST_Distance_Sphere(@pt1, @pt2, 1)

0.017453292519943295

SELECT ST_Distance_Sphere(@pt1, @pt2, NULL);

ST_Distance_Sphere(@pt1, @pt2, NULL)

null

show warnings