add jar datasketches-memory-2.0.0.jar;
add jar datasketches-java-3.1.0.jar;
add jar datasketches-hive-1.2.0.jar;

create temporary function data2sketch as 'org.apache.datasketches.hive.tuple.DataToArrayOfDoublesSketchUDAF';
create temporary function unionSketches as 'org.apache.datasketches.hive.tuple.UnionArrayOfDoublesSketchUDAF';
create temporary function estimate as 'org.apache.datasketches.hive.tuple.ArrayOfDoublesSketchToEstimatesUDF';

use <your-db-name-here>;

create temporary table tuple_input (id int, category char(1), parameter double);
insert into table tuple_input values
  (1, 'a', 1), (2, 'a', 1), (3, 'a', 1), (4, 'a', 1), (5, 'a', 1), (6, 'a', 1), (7, 'a', 1), (8, 'a', 1), (9, 'a', 1), (10, 'a', 1),
  (6, 'b', 1), (7, 'b', 1), (8, 'b', 1), (9, 'b', 1), (10, 'b', 1), (11, 'b', 1), (12, 'b', 1), (13, 'b', 1), (14, 'b', 1), (15, 'b', 1);

create temporary table sketch_intermediate (category char(1), sketch binary);
insert into sketch_intermediate select category, data2sketch(id, parameter) from tuple_input group by category;

-- estimates per category
select category, estimate(sketch) from sketch_intermediate;

Output:
a	[10.0,10.0]
b	[10.0,10.0]

-- union across categories and get estimates
select estimate(unionSketches(sketch)) from sketch_intermediate;

Output:
[15.0,20.0]