ST_LineStringAggr method

Returns a linestring built from the ordered points in a group.

Syntax

ST_LineString::ST_LineStringAggr(point[ ORDER BY order-by-expression [ ASC | DESC ], ... ] )

Parameters

Name	Type	Description
point	ST_Point	The points to generate the linestring. Typically this is a column.

Returns

ST_LineString Returns a linestring built from the points in a group.
The spatial reference system identifier of the result is the same as that for the first parameter.

The ST_LineStringAggr aggregate method can be used to build a linestring out of a group of ordered points. All of the geometry columns to be combined must have the same SRID. All of the points to be combined must be non-empty with the same coordinate dimension.

Rows where the point is NULL are not included.

Returns NULL for an empty group or a group containing no non-NULL values.

The resulting linestring has the same coordinate dimension as each point.

Note

The ORDER BY clause should be specified to control the order of points within the linestring. If not present, the order of points in the linestring will vary depending on the access plan selected by the query optimizer.

Note

By default, ST_LineStringAggr 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.

Standards and compatibility

Example

The following example returns the result LineString (0 0, 2 0, 1 1).

BEGIN 
    DECLARE LOCAL TEMPORARY TABLE t_points( pk INT PRIMARY KEY,
                                            p ST_Point );
    INSERT INTO t_points VALUES( 1, 'Point( 0 0 )' );
    INSERT INTO t_points VALUES( 2, 'Point( 2 0 )' );
    INSERT INTO t_points VALUES( 3, 'Point( 1 1 )' );

    SELECT ST_LineString::ST_LineStringAggr( p ORDER BY pk )
    FROM t_points;
END

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