add some sql functions

mariadb/deg2rad.sql

@@ -0,0 +1,4 @@
+CREATE OR REPLACE FUNCTION `deg2rad`(
+		deg DOUBLE
+	) RETURNS double
+RETURN deg * pi()/ 180;

mariadb/distance.sql

@@ -0,0 +1,16 @@
+CREATE OR REPLACE FUNCTION `distance`(
+	lon1 DOUBLE,
+	lat1 DOUBLE,
+	lon2 DOUBLE,
+	lat2 DOUBLE
+) RETURNS double
+BEGIN
+	SET @earth_radius = 6371;
+	SET @dLat = deg2rad(lat2-lat1);
+	SET @dLon = deg2rad(lon2-lon1);
+	SET lat1 = deg2rad(lat1);
+    SET lat2 = deg2rad(lat2);
+	SET @a = SIN(@dLat/2) * SIN(@dLat/2) + SIN(@dLon/2) * SIN(@dLon/2) * COS(lat1) * COS(lat2);
+	SET @c = 2 * ATAN2(SQRT(@a), SQRT(1-@a));
+	RETURN @earth_radius * @c;
+END;

mariadb/gauss.sql

@@ -0,0 +1,12 @@
+CREATE OR REPLACE FUNCTION `gauss`(
+		x DOUBLE,
+		c DOUBLE,
+		sig DOUBLE
+	) RETURNS double
+RETURN EXP(
+		(
+			- 1 * POWER(( x - c ), 2 )/(
+				2 * POWER( sig, 2 )
+			)
+		)
+	);

mariadb/get_bearing.sql

@@ -0,0 +1,16 @@
+CREATE OR REPLACE FUNCTION `get_bearing`(
+	lon1 DOUBLE,
+	lat1 DOUBLE,
+	lon2 DOUBLE,
+	lat2 DOUBLE
+) RETURNS double
+BEGIN
+	SET @rlat1 = deg2rad(lat1);
+	SET @rlat2 = deg2rad(lat2);
+	SET @rlon1 = deg2rad(lon1);
+	SET @rlon2 = deg2rad(lon2);
+	SET @dlon = deg2rad(lon2 - lon1);
+	SET @b = atan2(sin(@dlon) * cos(@rlat2), cos(@rlat1) * sin(@rlat2) - sin(@rlat1) * cos(@rlat2) * cos(@dlon)); 
+	SET @bd = rad2deg(@b);
+	RETURN MOD(@bd + 360, 360);
+END;

mariadb/rad2deg.sql

@@ -0,0 +1,4 @@
+CREATE OR REPLACE FUNCTION `rad2deg`(
+		rad DOUBLE
+	) RETURNS double
+RETURN rad * 180.0 / pi();