--disable_warnings
DROP DATABASE IF EXISTS MCOL5889;
--enable_warnings
CREATE DATABASE MCOL5889;
USE MCOL5889;

CREATE TABLE t1 (f1 DECIMAL, f2 BIGINT, f3 DOUBLE) ENGINE=columnstore;
CREATE TABLE t2 (f1 DECIMAL, f2 INT, f3 DOUBLE) ENGINE=columnstore;
INSERT INTO t1 VALUES (1, 2, 3), (2, 3, 4), (3, 4, 5);
INSERT INTO t2 VALUES (4, 5, 6), (5, 6, 7), (6, 7, 8);

--sorted_result
SELECT f1, f2, f3, f2 * f3 FROM
(
  SELECT f1, f2, AVG(f3) f3 FROM
  (
    SELECT f1, f2, f3 FROM t1
    UNION ALL
    SELECT f1, f2, f3 FROM t2
  ) U
  GROUP BY f1
) V;

DROP DATABASE MCOL5889;