Pues algo estás escribiendo mal...
Código SQL:
Ver originalmysql> DROP TABLE IF EXISTS table1;
Query OK, 0 ROWS affected (0.05 sec)
mysql> DROP TABLE IF EXISTS table2;
Query OK, 0 ROWS affected (0.05 sec)
mysql> CREATE TABLE table1(id_table1 INT UNSIGNED AUTO_INCREMENT PRIMARY KEY, texto VARCHAR(1000));
Query OK, 0 ROWS affected (0.09 sec)
mysql> CREATE TABLE table2(id_table2 INT UNSIGNED AUTO_INCREMENT PRIMARY KEY, fuente VARCHAR(100));
Query OK, 0 ROWS affected (0.11 sec)
mysql> INSERT INTO table2(fuente) VALUES('Pepe, Feliz 1066');
Query OK, 1 ROW affected (0.03 sec)
mysql> INSERT INTO table1(id_table1, texto) VALUES(1066, 'Texto de prueba');
Query OK, 1 ROW affected (0.03 sec)
mysql> SELECT * FROM table2 INNER JOIN table1 WHERE table2.fuente LIKE CONCAT('%', table1.id_table1, '%');
+-----------+------------------+-----------+-----------------+
| id_table2 | fuente | id_table1 | texto |
+-----------+------------------+-----------+-----------------+
| 1 | Pepe, Feliz 1066 | 1066 | Texto de prueba |
+-----------+------------------+-----------+-----------------+
1 ROW IN SET (0.00 sec)