STCurveN (geometry Data Type)
Returns the curve specified from a geometry instance that is a LineString, CircularString, CompoundCurve, or MultiLineString.
Syntax
.STCurveN ( curve_index )
Arguments
- curve_index
Is an int expression between 1 and the number of curves in the geometry instance.
Return Types
SQL Server return type: geometry
CLR return type: SqlGeometry
Exceptions
If curve_index < 1 then an ArgumentOutOfRangeException is thrown.
Remarks
NULL is returned when any of the following occurs:
the geometry instance is declared, but not instantiated
the geometry instance is empty
curve_index exceeds the number of curves in the geometry instance
the geometry instance is a Point, MultiPoint, Polygon, CurvePolygon, or MultiPolygon
Examples
A. Using STCurveN() on a CircularString instance
The following example returns the second curve in a CircularString instance:
DECLARE @g geometry = 'CIRCULARSTRING(0 0, 1 2.1082, 3 6.3246, 0 7, -3 6.3246, -1 2.1082, 0 0)';
SELECT @g.STCurveN(2).ToString();
The example earlier in this topic returns:
CIRCULARSTRING (3 6.3246, 0 7, -3 6.3246)
B. Using STCurveN() on a CompoundCurve instance with one CircularString instance
The following example returns the second curve in a CompoundCurve instance:
DECLARE @g geometry = 'COMPOUNDCURVE(CIRCULARSTRING(0 0, 1 2.1082, 3 6.3246, 0 7, -3 6.3246, -1 2.1082, 0 0))';
SELECT @g.STCurveN(2).ToString();
The example earlier in this topic returns:
CIRCULARSTRING (3 6.3246, 0 7, -3 6.3246)
C. Using STCurveN() on a CompoundCurve instance with three CircularString instances
The following example uses a CompoundCurve instance that combines three separate CircularString instances into the same curve sequence as the previous example:
DECLARE @g geometry = 'COMPOUNDCURVE (CIRCULARSTRING (0 0, 1 2.1082, 3 6.3246), CIRCULARSTRING(3 6.3246, 0 7, -3 6.3246), CIRCULARSTRING(-3 6.3246, -1 2.1082, 0 0))';
SELECT @g.STCurveN(2).ToString();
The example earlier in this topic returns:
CIRCULARSTRING (3 6.3246, 0 7, -3 6.3246)
Notice that the results are the same for the previous three examples. Whichever WKT (Well-known Text) format is used to enter the same curve sequence, the results returned by STCurveN() are the same when a CompoundCurve instance is used.
D. Validating the parameter before calling STCurveN()
The following example shows how to make sure @n is valid before you call the STCurveN()method:
DECLARE @g geometry;
DECLARE @n int;
SET @n = 3;
SET @g = geometry::Parse('CIRCULARSTRING(0 0, 1 2.1082, 3 6.3246, 0 7, -3 6.3246, -1 2.1082, 0 0)');
IF @n >= 1 AND @n <= @g.STNumCurves()
BEGIN
SELECT @g.STCurveN(@n).ToString();
END
See Also
Reference
STNumCurves (geometry Data Type)