STTouches (geometry Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Returns 1 if a geometry instance spatially touches another geometry instance. Returns 0 if it does not.
Syntax
.STTouches ( other_geometry )
Arguments
other_geometry
Is another geometry instance to compare against the instance on which STTouches() is invoked.
Return Types
SQL Server return type: bit
CLR return type: SqlBoolean
Remarks
Two geometry instances touch if their point sets intersect, but their interiors do not intersect.
This method always returns null if the spatial reference IDs (SRIDs) of the geometry instances do not match.
Examples
The following example uses STTouches() to test two geometry instances to see if they touch.
DECLARE @g geometry;
DECLARE @h geometry;
SET @g = geometry::STGeomFromText('LINESTRING(0 2, 2 0, 4 2)', 0);
SET @h = geometry::STGeomFromText('POINT(1 1)', 0);
SELECT @g.STTouches(@h);