ShortestLineTo (geometry Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
SQL database in Microsoft Fabric
Returns a LineString instance with two points that represent the shortest distance between the two geometry instances. The length of the LineString instance returned is the distance between the two geometry instances.
Syntax
.ShortestLineTo ( geometry_other )
Arguments
geometry_other
The second geometry instance that the calling geometry instance is trying to determine the shortest distance to.
Return Types
SQL Server return type: geometry
CLR return type: SqlGeometry
Remarks
The method returns a LineString instance with endpoints lying on the borders of the two non-intersecting geometry instances being compared. The length of the LineString returned equals the shortest distance between the two geometry instances. An empty LineString instance is returned when the two geometry instances intersect each other.
Examples
A. Calling ShortestLineTo() on non-intersecting instances
This example finds the shortest distance between a CircularString instance and a LineString instance and returns the LineString instance connecting the two points:
DECLARE @g1 geometry = 'CIRCULARSTRING(0 0, 1 2.1082, 3 6.3246, 0 7, -3 6.3246, -1 2.1082, 0 0)';
DECLARE @g2 geometry = 'LINESTRING(-4 7, 7 10, 3 7)';
SELECT @g1.ShortestLineTo(@g2).ToString();
B. Calling ShortestLineTo() on intersecting instances
This example returns an empty LineString instance because the LineString instance intersects the CircularString instance:
DECLARE @g1 geometry = 'CIRCULARSTRING(0 0, 1 2.1082, 3 6.3246, 0 7, -3 6.3246, -1 2.1082, 0 0)';
DECLARE @g2 geometry = 'LINESTRING(0 5, 7 10, 3 7)';
SELECT @g1.ShortestLineTo(@g2).ToString();