SQL 2008 geography & geometry - which to use?

Question

I'm creating a Google map mashup and am using SQL 2008.

I will have a large number of points on the earth and will want to perform various calculations on them in SQL - such as selecting all points contained within a particular polygone, or select all points within 10km of XY.

I have never used and SQL spatial features before. Should I use the geography or the geometry datatype for this?

Answer 1

Geography is the type that is intended for plotting points on the earth.

If you have a table that stores Google Maps points like this:

CREATE TABLE geo_locations (
    location_id       uniqueidentifier  NOT NULL,
    position_point    geography         NOT NULL
);

then you could fill points in it with this stored procedure:

CREATE PROCEDURE proc_AddPoint
    @latitude     decimal(9,6),
    @longitude    decimal(9,6),
    @altitude     smallInt
AS

DECLARE @point     geography = NULL;

BEGIN

    SET NOCOUNT ON;

    SET @point = geography::STPointFromText('POINT(' + CONVERT(varchar(15), @longitude) + ' ' + 
                                                       CONVERT(varchar(15), @latitude) + ' ' + 
                                                       CONVERT(varchar(10), @altitude) + ')', 4326)

    INSERT INTO geo_locations
    (
        location_id, 
        position_point
    )
    VALUES 
    (
        NEWID(),
        @point
    );

END

Then if you want to query for the latitude, longitude and altitude, simply use the following query format:

SELECT
    geo_locations.position_point.Lat  AS latitude,
    geo_locations.position_point.Long AS longitude,
    geo_locations.position_point.Z    AS altitude
FROM
    geo_locations;