Re: How can I selet rows which have 2 columns values cross equal?

On Mar 11, 2006, at 16:46 , Michael Glaesemann wrote:

> select t1.id as t1_id, t2.id as t2_id
> from test t1
> join test t2 on (t1.a = t2.b and t1.b = t2.a)
> where t1.a < t2.a;
> t1_id | t2_id
> -------+-------
> 4 | 7
> 1 | 2
> (2 rows)

Just a follow-up (mostly to myself): I've been toying with using
natural joins recently, and here's the same query rewritten to use a
natural join:

select id as t1_id, t2_id
from test t1
natural join (
select id as t2_id
, a as b
, b as a
from test
) t2
where id < t2_id;
t1_id | t2_id
-------+-------
4 | 7
1 | 2
(2 rows)

Michael Glaesemann
grzm myrealbox com