Categories:: Geospatial functions

ST_UNION_AGG¶

Given a GEOGRAPHY column, returns a GEOGRAPHY object that represents the combined set of points that are in at least one of the shapes represented by the objects in the column (that is, the union of the shapes).

See also:: ST_UNION , ST_INTERSECTION_AGG

Syntax¶

ST_UNION_AGG( <geography_column> )

Arguments¶

geography_column: A GEOGRAPHY column.

Returns¶

The function returns a value of type GEOGRAPHY.

Examples¶

Create a table with a GEOMETRY column and insert data:

CREATE OR REPLACE TABLE st_union_agg_demo_table (g GEOGRAPHY);

INSERT INTO st_union_agg_demo_table VALUES
  ('POINT(1 1)'),
  ('POINT(0 1)'),
  ('LINESTRING(0 0, 0 1)'),
  ('LINESTRING(0 0, 0 2)'),
  ('POLYGON((10 10, 11 11, 11 10, 10 10))'),
  ('POLYGON((10 10, 11 11, 11 10, 10 10))');

Use the ST_UNION_AGG function to return a GEOGRAPHY object that represents the combined set of points that are in at least one of the shapes represented by the objects in the GEOGRAPHY column:

ALTER SESSION SET GEOGRAPHY_OUTPUT_FORMAT = 'WKT';

SELECT ST_UNION_AGG(g) AS union_of_shapes
  FROM st_union_agg_demo_table;

+-------------------------------------------------------------------------------------------+
| UNION_OF_SHAPES                                                                           |
|-------------------------------------------------------------------------------------------|
| GEOMETRYCOLLECTION(POINT(1 1),LINESTRING(0 0,0 1,0 2),POLYGON((11 10,11 11,10 10,11 10))) |
+-------------------------------------------------------------------------------------------+