How can I query SQL Server database for the nearest store in a visitor's neighborhood?

Question

I have a list of stores each store has data like street_address, longitude, latitude.

Now, when a user visits my site, I want to show him/her all available stores in their neighborhood (within 10 miles radios "closest to furthest")

Here is what I have done. I create a new column called StPoint with the type geography . I used the geography::Point(latitude, longitude, 4326) function to convert the longitude/latitude of each store to a point like so

UPDATE stores 
SET StPoint = CASE WHEN latitude IS NOT NULL AND longitude IS NOT NULL
    THEN geography::Point(latitude, longitude, 4326)
    ELSE NULL END

I tried to find the distance between the visitor's current point and all the stores like so

SELECT 
 CASE WHEN StPoint IS NOT NULL THEN StPoint.STIntersection( geography::Point(42.2974416, -71.4478897, 4326) ).STAsText() ELSE NULL END AS distance
FROM stores

But this is giving me something like

GEOMETRYCOLLECTION EMPTY

or something like this

POINT (-99.4478897 56.2974416)

Finally, I tried using STDistance function which is returning a value (I am not sure what unit is used here)

SELECT StPoint.STDistance(geography::Point(42.2974416, -71.4478897, 4326))
FROM stores

Here are sample of what the above query shows

27376.5070395886
3973.49722397033
27620.9636451663
50346.8940144233
7425.98548351235
34193.3513625182

As you can see, the results is not in miles. How can I correctly get the closest store along with how far form the visitor each store is?

Answer 1

It looks like STDistance returns values in Geog unit. to convert it to Miles you'll need to divide vy 1609.344 (1 mile = 1609.344 meters)

SQL Server 2008 GEOGRAPHY STDistance() value

Try the following

SELECT StPoint.STDistance(geography::Point(42.2974416, -71.4478897, 4326))/1609.344
FROM stores