create table test(tok char(1) not null, count int(1) not null, key(tok))

create table test2(tok char(1) not null, count int(1)not null, key(tok))

create table test_merge (tok char(1)not null, count int(1) not null, key(tok)) type=merge union=(test,test2)

SELECT tok, sum(count) FROM `test_merge` WHERE 1 group by tok