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How to remove duplicates in an array and maintain the order?
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* How to remove duplicates in an array and maintain the order?
@ 2023-07-08 15:30  Shaozhong SHI <[email protected]>
  0 siblings, 3 replies; 4+ messages in thread

From: Shaozhong SHI @ 2023-07-08 15:30 UTC (permalink / raw)
  To: pgsql-sql <[email protected]>

How to remove duplicated values in an array and maintain the order?

Regards,

David


^ permalink  raw  reply  [nested|flat] 4+ messages in thread

* Re: How to remove duplicates in an array and maintain the order?
@ 2023-07-08 15:36  David G. Johnston <[email protected]>
  parent: Shaozhong SHI <[email protected]>
  2 siblings, 0 replies; 4+ messages in thread

From: David G. Johnston @ 2023-07-08 15:36 UTC (permalink / raw)
  To: Shaozhong SHI <[email protected]>; +Cc: pgsql-sql <[email protected]>

On Sat, Jul 8, 2023 at 8:30 AM Shaozhong SHI <[email protected]> wrote:

> How to remove duplicated values in an array and maintain the order?
>

Use a for loop in pl/pgsql.

David J.


^ permalink  raw  reply  [nested|flat] 4+ messages in thread

* Re: How to remove duplicates in an array and maintain the order?
@ 2023-07-08 15:50  Marcos Pegoraro <[email protected]>
  parent: Shaozhong SHI <[email protected]>
  2 siblings, 0 replies; 4+ messages in thread

From: Marcos Pegoraro @ 2023-07-08 15:50 UTC (permalink / raw)
  To: Shaozhong SHI <[email protected]>; +Cc: pgsql-sql <[email protected]>

>
> How to remove duplicated values in an array and maintain the order?
>
> select array_agg(unnest) filter (where row_number = 1) from (select
unnest, ordinality, row_number() over(partition by unnest order by
ordinality) from (select * from
unnest('{7,7,5,6,2,2,3,8,5,4,5}'::integer[]) with ordinality) x order by
ordinality) x

{7,5,6,2,3,8,4}

regards
Marcos


^ permalink  raw  reply  [nested|flat] 4+ messages in thread

* Re: How to remove duplicates in an array and maintain the order?
@ 2023-07-08 16:19  Thomas Kellerer <[email protected]>
  parent: Shaozhong SHI <[email protected]>
  2 siblings, 0 replies; 4+ messages in thread

From: Thomas Kellerer @ 2023-07-08 16:19 UTC (permalink / raw)
  To: [email protected]



Shaozhong SHI schrieb am 08.07.2023 um 17:30:
> How to remove duplicated values in an array and maintain the order?

You can use distinct on ()

select array_agg(val order by idx)
from (
   select distinct on (val) val, idx
   from unnest(array[7,7,5,6,2,2,3,8,7,5,4,1,5]) with ordinality as t(val,idx)
   order by val, idx
) x


This picks the first occurrance of each element.
If you want to get the last occurrance of each value use "order by val, idx desc" in the inner select








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Thread overview: 4+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2023-07-08 15:30 How to remove duplicates in an array and maintain the order? Shaozhong SHI <[email protected]>
2023-07-08 15:36 ` David G. Johnston <[email protected]>
2023-07-08 15:50 ` Marcos Pegoraro <[email protected]>
2023-07-08 16:19 ` Thomas Kellerer <[email protected]>

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