Array combinations without repetition

问题

I would like to make combinations out from an int[]

{2,4,6,7,8,10,13,15,16,18} should give following results:

2,4,6
2,4,7
2,4,8
...
15,16,18

Is it possible to write query only solution without using custom functions?

回答1:

with a as (
    select i
    from unnest (array[2,4,6,7,8,10,13,15,16,18]) s(i)
)
select *
from
    a cross join a b cross join a c
where
    a < b and b < c
order by a, b, c

来源：https://stackoverflow.com/questions/16899760/array-combinations-without-repetition