Point
In SQL Server spatial data, a Point is a 0-dimensional object representing a single location and may contain Z (elevation) and M (measure) values.
Geography Data Type
The Point type for the geography data type represents a single location where Lat represents latitude and Long represents longitude. The values for latitude and longitude are measured in degrees. Values for latitude always lie in the interval [-90, 90], and values that are inputted outside this range will throw an exception. Values for longitude always lie in the interval (-180, 180], and values inputted outside this range are wrapped around to fit in this range. For example, if 190 is inputted for longitude, then it will be wrapped to the value -170. SRID represents the spatial reference ID of the geography instance that you wish to return.
Geometry Data Type
The Point type for the geometry data type represents a single location where X represents the X-coordinate of the Point being generated and Y represents the Y-coordinate of the Point being generated. SRID represents the spatial reference ID of the geometry instance that you wish to return.
Examples
The following example creates a geometry Point instance representing the point (3, 4) with an SRID of 0.
DECLARE @g geometry;
SET @g = geometry::STGeomFromText('POINT (3 4)', 0);
The next example creates a geometry Point instance representing the point (3, 4) with a Z (elevation) value of 7, an M (measure) value of 2.5, and the default SRID of 0.
DECLARE @g geometry;
SET @g = geometry::Parse('POINT(3 4 7 2.5)');
The final example returns the X, Y, Z, and M values for the geometry Point instance.
SELECT @g.STX;
SELECT @g.STY;
SELECT @g.Z;
SELECT @g.M;
Z and M values may be explicitly specified as NULL, as shown in the following example.
DECLARE @g geometry;
SET @g = geometry::Parse('POINT(3 4 NULL NULL)');