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_posts/2013-03-05-haversine-in-mysql.markdown

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+---
+layout:    post
+title:     "Haversine in MySQL"
+date:      2013-03-05 12:49:28+00:00
+permalink: /blog/2013/3/5/haversine-in-mysql
+tags:      [mysql, development]
+published: true
+author:
+    name: Gergely Polonkai
+    email: gergely@polonkai.eu
+---
+
+Just insert it in your database, feed them two Google coordinates, and you get
+the distance in kilometres. If you happen to need it in miles, change the
+constant `12756.200` in the `RETURN` row to `7922.6` instead.
+
+{% highlight sql %}
+DELIMITER $$
+
+CREATE FUNCTION `haversine` (lng1 FLOAT, lat1 FLOAT, lng2 FLOAT, lat2 FLOAT)
+RETURNS float NO SQL DETERMINISTIC
+BEGIN
+    SET @a = ABS(POWER(SIN(RADIANS(lat1 - lat2)) / 2, 2) + COS(RADIANS(lat1)) * COS(RADIANS(lat2)) * POWER(SIN(RADIANS(lng1 - lng2)) / 2, 2));
+    RETURN 12756.200 * ATAN2(SQRT(@a), SQRT(1 - @a));
+END$$
+{% endhighlight %}