Kan du definere bogstavelige tabeller i SQL?

Jeg formoder, at du kunne lave en underforespørgsel med flere SELECT s kombineret med UNION s.

SELECT a, b, c, d
FROM (
    SELECT 1 AS a, 2 AS b, 3 AS c, 4 AS d
    UNION ALL 
    SELECT 5 , 6, 7, 8
) AS temp;