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?
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;