DROP TABLE IF EXISTS test1;
DROP TABLE IF EXISTS test2;
DROP TABLE IF EXISTS test3;

CREATE TABLE test1 (incr int not null, othr int not null, primary key(incr));
CREATE TABLE test2 (incr int not null, othr int not null, primary key(incr));
CREATE TABLE test3 (incr int not null, othr int not null, primary key(incr))
TYPE=MERGE UNION=(test1,test2);

@r/mrg000001.dummy.result SELECT * from test3;

INSERT INTO test1 VALUES ( 1,10),( 3,53),( 5,21),( 7,12),( 9,17);
INSERT INTO test2 VALUES ( 2,24),( 4,33),( 6,41),( 8,26),( 0,32);
INSERT INTO test1 VALUES (11,20),(13,43),(15,11),(17,22),(19,37);
INSERT INTO test2 VALUES (12,25),(14,31),(16,42),(18,27),(10,30);

@r/mrg000001.result SELECT * from test3 where incr in (1,2,3,4) order by othr;

DROP TABLE IF EXISTS test3;
DROP TABLE IF EXISTS test1;
DROP TABLE IF EXISTS test2;