STNumPoints (geometry Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Returns the sum of the number of points in each of the figures in a geometry instance.
Syntax
.STNumPoints ( )
Return Types
SQL Server return type: int
CLR return type: SqlInt32
Remarks
This method counts the points in the description of a geometry instance. Duplicate points are counted. If this instance is a collection type, this method returns the sum of the points in each of its elements.
Examples
The following example creates a LineString instance and uses STNumPoints() to determine how many points were used in the description of the instance.
DECLARE @g geometry;
SET @g = geometry::STGeomFromText('LINESTRING(0 0, 2 2, 1 0)', 0);
SELECT @g.STNumPoints();