radius search by latitude / longitude

I think you want POWER not POW

http://msdn.microsoft.com/en-us/library/ms174276.aspx

DECLARE @CurrentLocation geography; 
SET @CurrentLocation  = geography::Point(12.822222, 80.222222, 4326)

SELECT * , Round (GeoLocation.STDistance(@CurrentLocation ),0) AS Distance FROM [Landmark]
WHERE GeoLocation.STDistance(@CurrentLocation )<= 2000 -- 2 Km

Wonderful Tutorial

http://www.sql-server-helper.com/sql-server-2008/convert-latitude-longitude-to-geography-point.aspx

Since you're on SQL 2008, consider using the native geospatial capabilities. You can do fancy things like:

• Create a persisted computed column of geography type that represents your point.
• Create a spatial index on the computed column. This will make things like yourPoint.STDistance(@otherPoint) <= @distance efficient

Like so:

alter table [yourTable] add [p] as geography::Point(Latitude, Longitude, 4326) persisted;
create spatial index [yourSpatialIndex] on [yourTable] ([p])

declare @Latitude float = <somevalue>, @Longitude float = <somevalue>;
declare @point geography = geography::Point(@Latitude, @Longitude, 4326);
declare @distance int = <distance in meters>;

select * from [yourTable] where @point.STDistance([p]) <= @distance;