SET NAMES gb2312;

CREATE TABLE `o` (
  `id` int(11) default NULL,
  `name` varchar(11) default NULL
) TYPE=MyISAM;

insert into `o` values ('11','數(shù)據(jù)1');
insert into `o` values ('22','數(shù)據(jù)2');
insert into `o` values ('33','數(shù)據(jù)3');
insert into `o` values ('44','數(shù)據(jù)4');

CREATE TABLE `class1` (
  `id` int(11) default NULL,
  `name` varchar(11) default NULL
) TYPE=MyISAM;

insert into `class1` values ('11','數(shù)據(jù)3');
insert into `class1` values ('22','數(shù)據(jù)2');
insert into `class1` values ('33','數(shù)據(jù)4');
insert into `class1` values ('44','數(shù)據(jù)1');

CREATE TABLE `class2` (
  `id` int(11) default NULL,
  `name` varchar(50) default NULL
) TYPE=MyISAM;

insert into `class2` values ('11842542','子數(shù)據(jù)3');
insert into `class2` values ('22543253','子數(shù)據(jù)2');
insert into `class2` values ('33245235','子數(shù)據(jù)4');
insert into `class2` values ('44543254','子數(shù)據(jù)1');

SELECT *
, CONCAT(o.id, RIGHT(B.id, LENGTH(CAST( B.id AS CHAR)) - 2)) value
FROM class1 A, class2 B, o
where A.id = Left(B.id, 2)
and A.name = o.name;

+------+-------+----------+---------+------+-------+----------+
| id   | name  | id       | name    | id   | name  | value    |
+------+-------+----------+---------+------+-------+----------+
|   44 | 數(shù)據(jù)1  | 44543254 | 子數(shù)據(jù)1  |   11 | 數(shù)據(jù)1  | 11543254 |
|   22 | 數(shù)據(jù)2  | 22543253 | 子數(shù)據(jù)2  |   22 | 數(shù)據(jù)2  | 22543253 |
|   11 | 數(shù)據(jù)3  | 11842542 | 子數(shù)據(jù)3  |   33 | 數(shù)據(jù)3  | 33842542 |
|   33 | 數(shù)據(jù)4  | 33245235 | 子數(shù)據(jù)4  |   44 | 數(shù)據(jù)4  | 44245235 |
+------+-------+----------+---------+------+-------+----------+
4 rows in set (0.00 sec)

UPDATE
class2
LEFT JOIN class1  ON class1.id = LEFT(class2.id, 2)
LEFT JOIN o ON class1.name = o.name
SET class2.ID = CONCAT(o.id, RIGHT(class2.id, LENGTH(CAST(class2.id AS CHAR)) - 2)) ;

Query OK, 3 rows affected (0.00 sec)
Rows matched: 4  Changed: 3  Warnings: 0

SELECT * FROM class2;

+----------+---------+
| id       | name    |
+----------+---------+
| 33842542 | 子數(shù)據(jù)3  |
| 22543253 | 子數(shù)據(jù)2  |
| 44245235 | 子數(shù)據(jù)4  |
| 11543254 | 子數(shù)據(jù)1  |
+----------+---------+
4 rows in set (0.00 sec)

DROP TABLE `o`;
DROP TABLE `class1`;
DROP TABLE `class2`;