MySQL cartesian product between two SELECT statements

Question

I want to perform a cartesian product between two SELECT statements as

SELECT 1, 2     INNER JOIN     SELECT 3, 4 ;

I expect the result to

Answer 1

mysql> select * from
    ->   (select 1 x union select 2 union select 3 union select 4) t
    ->   join
    ->   (select 1 y union select 2 union select 3) tt;
+---+---+
| x | y |
+---+---+
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
| 3 | 1 |
| 3 | 2 |
| 3 | 3 |
| 4 | 1 |
| 4 | 2 |
| 4 | 3 |
+---+---+
12 rows in set (0.00 sec)

Removing the word join gives exactly the same result.

select * from
  (select 1 x union select 2 union select 3 union select 4) t,
  (select 1 y union select 2 union select 3) tt;