Question

A SELECT without a FROM clause gets us a multiple columns without querying a table:

SELECT 17+23, REPLACE('bannanna', 'nn', 'n'), RAND(), CURRENT_TIMESTAMP;

How can we write a query that results in multiple rows without referring to a table? Basically, abuse SELECT to turn it into a data definition statement. The result could have a single column or multiple columns.

I’m most interested in a DBMS neutral answer, but others (e.g. based on UNPIVOT) are welcome. I’d like to collect as many ways of doing this as possible. There’s no technique application behind this question; it’s more theoretical than practical.

Answer 1

Use a UNION:

SELECT 1
UNION
SELECT 2

Looks like this in MySQL:

+---+
| 1 |
+---+
| 1 | 
| 2 | 
+---+

Use UNION ALL to avoid the loss of non-unique rows.