SQL 2003 Distance Latitude Longitude
- by J.Hendrix
I have a table full of Dealers along with their latitude and longitude. I am trying to determine the top n closest dealers to any given lat and lon. I already have the function to calculate distance between locations, but I want to do as few calculations as possible (my table can contain many thousands of entries). Currently I have to calculate the distance for each entry then sort them. Is there any way to sort before I do the calculation to improve performance?
This question is good, but I will not always know my range. Should I just pick an arbitrarily high range then refine my results? I am thankful for any help the community can offer.
declare @Lat real
declare @lon real
Set @lat = 41.05
Set @lon = -73.53
SELECT top 10
MemberID,
Address1,
City,
State,
Zip,
Phone,
Lat,
Lon,
(SELECT fun_DistanceLatLon] (@Lat,@lon,Lat,Lon)) as mDistance --Calculate distance
FROM
Dealers
Order by
(SELECT fun_DistanceLatLon] (@Lat,@lon,Lat,Lon))
