STAsText (geography Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
SQL database in Microsoft Fabric
Returns the Open Geospatial Consortium (OGC) Well-Known Text (WKT) representation of a geography instance. This text will not contain any Z (elevation) or M (measure) values carried by the instance.
This geography data type method supports FullGlobe instances or spatial instances that are larger than a hemisphere.
Syntax
.STAsText ( )
Return Types
SQL Server return type: nvarchar(max)
CLR return type: SqlChars
Remarks
The OGC type of a geography instance can be determined by invoking STGeometryType().
In SQL Server 2012 (11.x), the set of possible results returned on the server has been extended to FullGlobe instances.
Examples
The following example uses STAsText() to create a LineString``geography instance from (-122.360, 47.656) to (-122.343, 47.656) from text. It then returns the result in text.
DECLARE @g geography;
SET @g = geography::STGeomFromText('LINESTRING(-122.360 47.656, -122.343 47.656)', 4326);
SELECT @g.STAsText();