Interesting SQL quiz

Question

Recently I came across with the following quiz. Imagine we have this table

+--------+
| colors |
+--------+
| red    |
| black  |
| white  |
| green  |
| orange |
+--------+

The task is to write a SQL query that will select all pairs without allowing duplicates. Permutations are counted too ({red, black} = {black, red}, hence only one of the pair is allowed).

Answer 1

Try this

Select A.Color, B.Color
From Colors A
Cross Join Colors B
Where A.Color > B.Color