Re: Remove duplicate rows and order by number of occurences - Mailing list pgsql-novice

Hello,

I think you need something like ...

SELECT count(*), file_id
     FROM temp_tagged
     GROUP BY file_id
     HAVING count(*) > 1;

This will select only those records that are duplicated.

Carol

On Jan 29, 2009, at 12:04 PM, postgres-novice@coreland.ath.cx wrote:

> Hello.
>
> I'm trying to SELECT from the following table:
>
> file_id
> ---------
>       1
>       1
>       2
>       3
>       5
>       6
>       9
>       9
>       9
>      10
>      10
>
> The result I'm trying to achieve is essentially to order the
> file_id column, in descending order, by the number of times
> each row occurs with a given value. I would also like to remove
> duplicate rows. In other words, the above table becomes
> (approximately):
>
> file_id
> ---------
>       9
>      10
>       1
>       6
>       5
>       3
>       2
>
> The order of the last four values isn't significant (they occur
> an equal number of times).
>
> I thought that this might be the solution:
>
>  SELECT file_id FROM temp_tagged;
>    GROUP BY file_id
>    ORDER BY count (file_id) DESC;
>
> But apparently, it isn't.
>
> Any help would be appreciated.
>
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