Re: select only 1 pair

William Alves Da Silva <william_silva@unochapeco.edu.br>

From: William Alves Da Silva <william_silva@unochapeco.edu.br>

To: pgsql-sql <pgsql-sql@lists.postgresql.org>, Shaozhong SHI <shishaozhong@gmail.com>

Date: 2022-10-24T15:01:30Z

Lists: pgsql-sql

Hello David,

Try this.

This is an exemple of your table.
SELECT *
  FROM (VALUES (1, 2), (2, 1), (3, 4), (4, 1)) t (id1, id2)

id1   |id2   |
------+------+
     1|     2|
     2|     1|
     3|     4|
     4|     1|


I think that is what you need
SELECT DISTINCT LEAST(id1, id2) AS id1, GREATEST(id1, id2) AS id2
  FROM (VALUES (1, 2), (2, 1), (3, 4), (4, 3)) t (id1, id2)

id1   |id2   |
------+------+
     1|     2|
     3|     4|

Regards,

William Alves
On 24 Oct 2022 11:44 -0300, Shaozhong SHI <shishaozhong@gmail.com>, wrote:
> There are pair ids.  Each pair is repeated.
>
> id1   id2
> 1       2
> 2        1
> 3         4
> 4         3
>
> How to only select 1 unique pair for each?
>
> Regards,
>
> David