Awesome, thanks.

It might be good to put the radius of the earth as a constant at the top of the function (or initialised variable in SQL), so readers of the function can understand how it works, and change it to kilometers, or whatever. The number of degrees per radian (57.29...) would also make a good candidate for a constant since it is repeated several times.

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=radius%20of%20earth%20in%20miles