mysql>
mysql>
mysql> SELECT LETTER1 || LETTER2 || LETTER3
-> FROM (SELECT 'a' AS LETTER1 UNION SELECT 'b'
-> UNION SELECT 'c' UNION SELECT 'd') AS LETTERS1,
-> (SELECT 'a' AS LETTER2 UNION SELECT 'b'
-> UNION SELECT 'c' UNION SELECT 'd') AS LETTERS2,
-> (SELECT 'a' AS LETTER3 UNION SELECT 'b'
-> UNION SELECT 'c' UNION SELECT 'd') AS LETTERS3;
+-------------------------------+
| LETTER1 || LETTER2 || LETTER3 |
+-------------------------------+
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
+-------------------------------+
64 rows in set (0.00 sec)
mysql>