SQL Server Geospatial Data - Advanced Spatial Queries

Introduction

SQL Server provides powerful geospatial data capabilities for storing and querying geographic and geometric data. This guide explores advanced spatial query techniques, including sample code and examples.

1. Geometry and Geography Data Types

SQL Server supports two main geospatial data types: Geometry (for Euclidean, planar data) and Geography (for ellipsoidal, round-earth data). Understand the differences between these types.

-- Create a Point using Geometry
DECLARE @point geometry = geometry::Point(47.6197, -122.3231, 4326);
-- Create a Point using Geography
DECLARE @point geography = geography::Point(47.6197, -122.3231, 4326);
    

2. Spatial Indexing

To optimize spatial queries, consider creating spatial indexes on your geospatial columns.

-- Create a Spatial Index
CREATE SPATIAL INDEX SIndx
ON YourTable(YourGeometryColumn)
USING GEOGRAPHY_GRID
WITH (GRIDS = (LEVEL_1 = MEDIUM, LEVEL_2 = MEDIUM, LEVEL_3 = MEDIUM, LEVEL_4 = MEDIUM),
CELLS_PER_OBJECT = 16);
    

3. Basic Spatial Queries

Perform basic spatial queries to retrieve data points within specified distances or boundaries.

-- Find Points within a Radius
SELECT Name
FROM Places
WHERE Location.STDistance(@point) <= 10000;
    

4. Advanced Spatial Queries

Execute advanced spatial queries to perform operations like buffering, intersection, and more.

-- Buffer a Point
SELECT @point.STBuffer(1000);
    

5. Geospatial Functions

SQL Server provides a wide range of geospatial functions for working with geospatial data. Familiarize yourself with these functions to build complex queries.

-- Calculate the Area of a Polygon
SELECT YourPolygon.STArea();
    

Conclusion

SQL Server's geospatial capabilities are invaluable for applications that involve geographic or geometric data. By understanding geometry and geography data types, utilizing spatial indexing, mastering basic and advanced spatial queries, and leveraging geospatial functions, you can perform complex geospatial operations within your SQL Server database.