-- Two original tables
create table a (
  id int(11) unsigned not null,
  account_no bigint(26) unsigned not null,
  unique key id_idx (id)
);
create table b (
  id int(11) unsigned not null,
  balance double not null,
  unique key id_idx (id)
);
-- New table
create table c (
  id int(11) unsigned not null,
  account_no bigint(26) not null,
  balance float not null,
  unique key id_idx (id)
);
insert into a values (1,1);
insert into a values (2,2);
insert into b values (1,100.0);
insert into b values (2,200.0);

-- Populate c with values from a and b
insert into c (
  id,
  account_no,
  balance) 
select
  a.id,
  a.account_no,
  b.balance
from a, b
where a.id=b.id;

select * from c;
+----+------------+---------+
| id | account_no | balance |
+----+------------+---------+
|  1 |          1 |     100 |
|  2 |          2 |     200 |
+----+------------+---------+
2 rows in set (0.00 sec)