select st_union(shape) geom from base_layers.hl_huc

ERROR:  function st_union(st_geometry) does not exist
LINE 1: select st_union(shape) geom from base_layers.hl_huc
               ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
********** Error **********

ERROR: function st_union(st_geometry) does not exist
SQL state: 42883
Hint: No function matches the given name and argument types. You might need to add explicit type casts.
Character: 8

CREATE EXTENSION postgis;

select sde.ST_Aggr_Union(shape) as geom from base_layers.hl_huc