st_union function

Applies to: Databricks Runtime 17.1 and above

Returns the point-set union of the two input geometries as a 2D geometry.

Syntax

st_union ( geo1, geo2 )

Arguments

• geo1: The first GEOMETRY value.
• geo2: The second GEOMETRY value.

Returns

A value of type GEOMETRY, representing the point-set union of the two input geometries as a 2D geometry.

The SRID of the returned GEOMETRY value is the common SRID of the two input geometries.

The function returns NULL if any of the inputs is NULL.

Error conditions

• If the input geometries do not have the same SRID value, the function returns ST_DIFFERENT_SRID_VALUES.

Examples

-- Returns union of multipoint and polygon.
> SELECT st_astext(st_union(st_geomfromtext('MULTIPOINT(EMPTY,4 3,5 6,-1 8)'),st_geomfromtext('POLYGON((0 0,10 0,0 10,0 0))')))
  GEOMETRYCOLLECTION(POINT(-1 8),POINT(5 6),POLYGON((0 0,0 10,10 0,0 0)))
-- Returns union of two overlapping polygons.
> SELECT st_astext(st_union(st_geomfromtext('POLYGON((0 0,5 0,5 5,0 5,0 0))'),st_geomfromtext('POLYGON((3 3,8 3,8 8,3 8,3 3))')))
  POLYGON((5 3,5 0,0 0,0 5,3 5,3 8,8 8,8 3,5 3))

Related functions

• st_intersection function
• st_union_agg function