Name
ST_CurveN — Returns the Nth component curve geometry of a CompoundCurve.
Synopsis
geometry ST_CurveN(geometry a_compoundcurve, integer index);
Description
Returns the Nth component curve geometry of a CompoundCurve. The index starts at 1. Returns NULL if the geometry is not a CompoundCurve or the index is out of range.
This method implements the SQL/MM specification.
SQL-MM 3: 8.2.6, 8.3.5
This function supports 3d and will not drop the z-index.
Examples
This example extracts the second component curve, a CircularString, from a CompoundCurve.
Code
SELECT ST_CurveN(
'COMPOUNDCURVE(
(0 0,2 0),
CIRCULARSTRING(2 0,3 1,4 0),
(4 0,6 1)
)',
2) AS curve;
Output
CIRCULARSTRING(2 0,3 1,4 0)
Figure