经纬度距离计算

--计算地球上两个坐标点（经度，纬度）之间距离sql函数
--作者：lordbaby
--整理：www.aspbc.com 
-- dbo.GetDistance(用户经度,用户纬度,经度,纬度)
-- =============================================
CREATE FUNCTION [dbo].[GetDistance](@LatBegin REAL, @LngBegin REAL, @LatEnd REAL, @LngEnd REAL) RETURNS FLOAT
  AS
BEGIN
  DECLARE @Distance REAL
  DECLARE @EARTH_RADIUS REAL
  SET @EARTH_RADIUS = 6378.137  
  DECLARE @RadLatBegin REAL,@RadLatEnd REAL,@RadLatDiff REAL,@RadLngDiff REAL
  SET @RadLatBegin = @LatBegin *PI()/180.0  
  SET @RadLatEnd = @LatEnd *PI()/180.0  
  SET @RadLatDiff = @RadLatBegin - @RadLatEnd  
  SET @RadLngDiff = @LngBegin *PI()/180.0 - @LngEnd *PI()/180.0   
  SET @Distance = 2 *ASIN(SQRT(POWER(SIN(@RadLatDiff/2), 2)+COS(@RadLatBegin)*COS(@RadLatEnd)*POWER(SIN(@RadLngDiff/2), 2)))
  SET @Distance = @Distance * @EARTH_RADIUS
  RETURN @Distance
END
GO