SQL

drop function if exists entfernung;
delimiter //
create function entfernung(lat1 double, lon1 double, lat2 double, lon2 double)
	returns double
	language sql
	contains sql
	comment 'Berechnet die Entfernung zwischen zwei Koordinaten'
begin
	declare erdradius double;

	declare lambda1 double;
	declare phi1 double;

	declare lambda2 double;
	declare phi2 double;

	declare x1 double;
	declare y1 double;
	declare z1 double;

	declare x2 double;
	declare y2 double;
	declare z2 double;

	declare entfernung double;

	set erdradius = 6371;

	set lambda1 = lon1 * pi() / 180;
	set phi1 = lat1 * pi() / 180;

	set lambda2 = lon2 * pi() / 180;
	set phi2 = lat2 * pi() / 180;

	set x1 = erdradius * cos(phi1) * cos(lambda1);
	set y1 = erdradius * cos(phi1) * sin(lambda1);
	set z1 = erdradius * sin(phi1);

	set x2 = erdradius * cos(phi2) * cos(lambda2);
	set y2 = erdradius * cos(phi2) * sin(lambda2);
	set z2 = erdradius * sin(phi2);

	set entfernung = 2 * erdradius * asin(sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2) + pow(z1 - z2, 2)) / (2 * erdradius));

	return entfernung;
end;
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