Re: PL/PGSQL for permutations?

D. Stimits wrote:
> table field pair. E.G., if I had in table 'one':
> left  right
> ====  =====
> a     b
> a     c
> b     d
>
> ...then I'd need a list of a, b, c, d, and produce a new table:
> left  right
> ====  =====
> a     b
> a     c
> a     d
> b     a
> b     c
> b     d
> c     a
> c     b
> c     d
> d     a
> d     b
> d     c

I don't have 7.2 to test on (and you really should upgrade to 7.3.4 if
possible anyway), but why not:

create table t1(f1 text, f2 text);
insert into t1 values('a','b');
insert into t1 values('a','c');
insert into t1 values('b','d ');

select a, b
from
   (select distinct f1 as a from t1 union select distinct f2 from t1)
    as ss1,
   (select distinct f1 as b from t1 union select distinct f2 from t1)
    as ss2
where ss1.a != ss2.b;
  a  | b
----+----
  a  | b
  a  | c
  a  | d
  b  | a
  b  | c
  b  | d
  c  | a
  c  | b
  c  | d
  d  | a
  d  | b
  d  | c
(12 rows)

HTH,

Joe