Consulta de dos tablas ver sus datos de las dos

mysql> INSERT INTO personas2 (nombre, fecha) VALUES
    -> ("Fulanito", "1956-12-14"),
    -> ("Menganito", "1975-10-15"),
    -> ("Tulanita", "1985-03-17"),
    -> ("Fusganita", "1976-08-25");
Query OK, 4 rows affected (0.09 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM personas2;
+----+-----------+------------+
| id | nombre    | fecha      |
+----+-----------+------------+
|  1 | Fulanito  | 1956-12-14 |
|  2 | Menganito | 1975-10-15 |
|  3 | Tulanita  | 1985-03-17 |
|  4 | Fusganita | 1976-08-25 |
+----+-----------+------------+
4 rows in set (0.00 sec)

mysql>

Ahora insertaremos datos en la tabla de telefonos2:

mysql> INSERT INTO telefonos2 (id, numero) VALUES
    -> (1, "123456789"),
    -> (1, "145654854"),
    -> (1, "152452545"),
    -> (2, "254254254"),
    -> (4, "456545654"),
    -> (4, "441415414");
Query OK, 6 rows affected (0.06 sec)
Records: 6  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM telefonos2;
+-----------+---------+
| numero    | persona |
+-----------+---------+
| 123456789 |       1 |
| 145654854 |       1 |
| 152452545 |       1 |
| 254254254 |       2 |
| 456545654 |       4 |
| 441415414 |       4 |
+-----------+---------+
6 rows in set (0.00 sec)

mysql>

El producto cartesiano de dos tablas son todas las combinaciones de todas las filas de las dos tablas. Usando una sentencia SELECT se hace proyectando todos los atributos de ambas tablas. Los nombres de las tablas se indican en la cláusula FROM separados con comas:

mysql> SELECT * FROM personas2,telefonos2;
+----+-----------+------------+-----------+----+
| id | nombre    | fecha      | numero    | id |
+----+-----------+------------+-----------+----+
|  1 | Fulanito  | 1956-12-14 | 123456789 |  1 |
|  2 | Menganito | 1975-10-15 | 123456789 |  1 |
|  3 | Tulanita  | 1985-03-17 | 123456789 |  1 |
|  4 | Fusganita | 1976-08-25 | 123456789 |  1 |
|  1 | Fulanito  | 1956-12-14 | 145654854 |  1 |
|  2 | Menganito | 1975-10-15 | 145654854 |  1 |
|  3 | Tulanita  | 1985-03-17 | 145654854 |  1 |
|  4 | Fusganita | 1976-08-25 | 145654854 |  1 |
|  1 | Fulanito  | 1956-12-14 | 152452545 |  1 |
|  2 | Menganito | 1975-10-15 | 152452545 |  1 |
|  3 | Tulanita  | 1985-03-17 | 152452545 |  1 |
|  4 | Fusganita | 1976-08-25 | 152452545 |  1 |
|  1 | Fulanito  | 1956-12-14 | 254254254 |  2 |
|  2 | Menganito | 1975-10-15 | 254254254 |  2 |
|  3 | Tulanita  | 1985-03-17 | 254254254 |  2 |
|  4 | Fusganita | 1976-08-25 | 254254254 |  2 |
|  1 | Fulanito  | 1956-12-14 | 456545654 |  4 |
|  2 | Menganito | 1975-10-15 | 456545654 |  4 |
|  3 | Tulanita  | 1985-03-17 | 456545654 |  4 |
|  4 | Fusganita | 1976-08-25 | 456545654 |  4 |
|  1 | Fulanito  | 1956-12-14 | 441415414 |  4 |
|  2 | Menganito | 1975-10-15 | 441415414 |  4 |
|  3 | Tulanita  | 1985-03-17 | 441415414 |  4 |
|  4 | Fusganita | 1976-08-25 | 441415414 |  4 |
+----+-----------+------------+-----------+----+
24 rows in set (0.73 sec)