This chapter examines the methods and properties available to query individual items of geometry or geography data.
The following tables list the methods covered in this chapter. For each method, the book gives the syntax required to use that method, the results obtained, and an example code listing demonstrating a practical situation in which that method can be used. This chapter contains numerous diagrams to illustrate the results obtained from the methods available.
Properties that return individual coordinate values
| Property |
Description |
Supported Datatypes |
| STX |
Returns the x coordinate of a point |
geometry |
|
| STY |
Returns the y coordinate of a point |
geometry |
|
| Lat |
Returns the latitude coordinate of a point |
|
geography |
| Long |
Returns the longitude coordinate of a point |
|
geography |
| M |
Returns the m coordinate of a point |
geometry |
geography |
| Z |
Returns the z coordinate of a point |
geometry |
geography |
Methods that return individual points from a geometry
| Method |
Description |
Supported Datatypes |
| STPointN() |
Returns the nth point of a geometry |
geometry |
geography |
| STStartPoint() |
Returns the first point of a geometry |
geometry |
geography |
| STEndPoint() |
Returns the last point of a geometry |
geometry |
geography |
| STCentroid() |
Returns the geometric center point of a Polygon instance |
geometry |
|
| EnvelopeCenter() |
Returns the envelope centre point of a geography instance |
|
geography |
| STPointOnSurface() |
Returns an abitrary point that lies within a geometry |
geometry |
|
Describing a Geometry
| Method |
Description |
Supported Datatypes |
| STGeometryType() |
Returns the name of the type of geometry. (e.g., Point, LineString) |
geometry |
geography |
| InstanceOf() |
Tests whether an instance is of a particular geometry type |
geometry |
geography |
| STDimension() |
Returns the number of dimensions that an instance occupies |
geometry |
geography |
| STIsSimple() |
Determines whether an instance is simple |
geometry |
|
| STIsClosed() |
Determines whether an instance is closed |
geometry |
|
| STIsRing() |
Determines whether an instance is a ring |
geometry |
|
| STNumPoints() |
Counts the number of points in a geometry |
geometry |
geography |
| STIsEmpty() |
Determines whether an instance is empty |
geometry |
|
| STSrid |
Sets or retrieves the SRID of the spatial reference system in which an instance is defined |
geometry |
geography |
Metrics
| Method |
Description |
Supported Datatypes |
| STLength() |
Returns the length of a geometry |
geometry |
geography |
| STArea() |
Tests whether an instance is of a particular geometry type |
geometry |
geography |
Polygon Rings
| Method |
Description |
Supported Datatypes |
| STExteriorRing() |
Returns the exterior ring of a Polygon instance |
geometry |
|
| STNumInteriorRing() |
Returns the number of interior rings in a Polygon instance |
geometry |
|
| STInteriorRingN() |
Returns the nth interior ring of a Polygon instance |
geometry |
|
| NumRings() |
Returns the total number of rings in a Polygon instance |
|
geography |
| RingN() |
Returns the nth ring of a Polygon instance/td>
| |
geography |
Describing the extent of a geometry
| Method |
Description |
Supported Datatypes |
| STBoundary() |
Returns the boundary of an instance |
geometry |
|
| STEnvelope() |
Returns the envelope (bounding box) of an instance |
geometry |
|
| EnvelopeAngle() |
Returns the angle between the centre of a geography instance and the most outlying point |
|
geography |
Working with multielement geometries
| Method |
Description |
Supported Datatypes |
| STNumGeometries() |
Returns the number of geometries in an instance |
geometry |
geography |
| STGeometryN() |
Returns a specific geometry from a multielement geometry |
geometry |
geography |
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