ST_PointN method

Returns the nth point in the circularstring.

Note

By default, ST_PointN uses the original format for a geometry, if it is available. Otherwise, the internal format is used. For more information about internal and original formats, see STORAGE FORMAT clause, CREATE SPATIAL REFERENCE SYSTEM statement.

Syntax

circularstring-expression.ST_PointN(n)

Parameters

Name	Type	Description
n	INT	The position of the element to return, from 1 to circularstring-expression.ST_NumPoints().

Returns

ST_Point If the value of circular-expression is the empty set, returns NULL. If the specified position n is less than 1 or greater than the number of points, returns NULL. Otherwise, returns the ST_Point value at position n.
The spatial reference system identifier of the result is the same as the spatial reference system of the circularstring-expression.

Standards and compatibility

Example

The following example returns the result Point (2 0).

SELECT TREAT( Shape AS ST_CircularString ).ST_PointN( 3 )
FROM SpatialShapes WHERE ShapeID = 18

The following example returns one row for each point in geom.

BEGIN
    DECLARE geom ST_CircularString;
    SET geom = NEW ST_CircularString( 'CircularString( 0 0, 1 1, 2 0 )' );
    SELECT row_num, geom.ST_PointN( row_num )
        FROM sa_rowgenerator( 1, geom.ST_NumPoints() )
        ORDER BY row_num;
END

The example returns the following result set:

row_num	geom.ST_PointN(row_num)
`1`	`Point (0 0)`
`2`	`Point (1 1)`
`3`	`Point (2 0)`

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