From: | "Peter Childs" <peterachilds(at)gmail(dot)com> |
---|---|
To: | "Yi Zhao" <yi(dot)zhao(at)alibaba-inc(dot)com> |
Cc: | pgsql-general <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: how to remove the duplicate records from a table |
Date: | 2008-10-07 07:04:45 |
Message-ID: | a2de01dd0810070004m443e02e1xf3d9b6d5778758eb@mail.gmail.com |
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Lists: | pgsql-general |
2008/10/7 Yi Zhao <yi(dot)zhao(at)alibaba-inc(dot)com>:
> I have a table contains some duplicate records, and this table create
> without oids, for example:
> id | temp_id
> ----+---------
> 10 | 1
> 10 | 1
> 10 | 1
> 20 | 4
> 20 | 4
> 30 | 5
> 30 | 5
> I want get the duplicated records removed and only one is reserved, so
> the results is:
> 10 1
> 20 4
> 30 5
>
> I know create a temp table will resolve this problem, but I don't want
> this way:)
>
> can someone tell me a simple methold?
>
> any help is appreciated,
>
> thanks,
>
>
I would not say this is easier....
1. alter table t add key serial;
2. delete from table where key not in (select max(key) from table
group on id,temp_id);
The truth is this is not any less work then using a temporary table
(whole table still needs rewriting). Which method you select really
depends on why these duplicate records exist in the first place.
Regards
Peter
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