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From: William Alves Da Silva <[email protected]>
To: pgsql-sql <[email protected]>
To: Shaozhong SHI <[email protected]>
Subject: Re: select only 1 pair
Date: Mon, 24 Oct 2022 12:01:30 -0300
Message-ID: <7f09c27c-c4df-4836-bd29-706ebc5eb154@Spark> (raw)
In-Reply-To: <CA+i5Jwa5VR7vJ=9S-9-d_3HgxQ_MmqwLW9+vqeN=jNDUVSVCHQ@mail.gmail.com>
References: <CA+i5Jwa5VR7vJ=9S-9-d_3HgxQ_MmqwLW9+vqeN=jNDUVSVCHQ@mail.gmail.com>

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 <[email protected]>, 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

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