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Applies to: 
Databricks SQL Databricks Runtime 17.1 and above
Important
This feature is in Public Preview.
Note
This feature is not available on Databricks SQL Classic warehouses. To learn more about Databricks SQL warehouses, see SQL warehouse types
Returns the point-wise union of all the geometries in the column, or NULL if the column is zero rows, or contains only NULL values.
Syntax
st_union_agg ( geoCol )
Arguments
geoCol: A column ofBINARY,GEOMETRY, orSTRINGvalues representing geometry objects.
Returns
A value of type GEOMETRY, representing the point-wise union of all geometries in the column.
The output GEOMETRY is always two-dimensional.
The function returns NULL if the column has zero rows or contains only NULL values.
Error conditions
- If the input is
GEOMETRYand geometries have different SRID values, the function returns ST_DIFFERENT_SRID_VALUES.
Examples
-- Returns union of multiple geometries from column.
> SELECT st_astext(st_union_agg(st_geomfromtext(*))) FROM (SELECT * FROM VALUES('POINT(-5 -5)'),('MULTIPOINT(1 2,8 8,5 9,-7 -7,EMPTY)'),('MULTILINESTRING(EMPTY,(5 5,9 9),(9 9,15 15))'),('POLYGON((0 0,10 0,10 10,0 10,0 0))'));
GEOMETRYCOLLECTION(MULTIPOINT((-7 -7),(-5 -5)),LINESTRING(10 10,15 15),POLYGON((0 0,10 0,10 10,0 10,0 0)))
-- Returns NULL for empty result set.
> SELECT st_union_agg(st_geomfromtext(geom)) FROM (SELECT 'POINT(1 1)' as geom WHERE false);
NULL