STGeomFromText

STGeomFromText is a constructor used in SQL Server’s spatial types to create a geometry or geography instance from a Well-Known Text (WKT) representation. It is provided as a static method on both the geometry and geography data types and requires two arguments: a WKT string and an integer SRID that defines the spatial reference system.

There are two supported forms of the function. For geometry, use geometry::STGeomFromText(wellKnownText, srid). For geography, use geography::STGeomFromText(wellKnownText, srid). Each form returns an instance of its respective spatial type, constructed from the given WKT and SRID.

The WKT input must conform to the Well-Known Text standard. Examples include 'POINT (30 10)', 'LINESTRING (30 10, 10 30, 40 40)', and 'POLYGON ((30 10, 40 40, 20 40, 10 20, 30 10))'. For geography, coordinates are usually provided in longitude and latitude according to the specified SRID, with 4326 (WGS 84) being the common default.

SRID specifies the spatial reference system used for the geometry or geography. A valid SRID is required, and common values include 4326 for global GPS coordinates. An invalid WKT or an invalid SRID will result in an error when the function is executed.

Examples of usage include: SELECT geometry::STGeomFromText('POINT (1 2)', 0); and SELECT geography::STGeomFromText('POINT(-122.349 47.651)', 4326). After construction, the resulting object can be used with other spatial methods such as STAsText, STDistance, or STIntersects. STGeomFromText complements other constructors like STGeomFromWKB for binary inputs.