From: | Dave Potts <dave(dot)potts(at)pinan(dot)co(dot)uk> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: returning only part of a rule set |
Date: | 2014-11-25 22:56:14 |
Message-ID: | 5475090E.6090304@pinan.co.uk |
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Thread: | |
Lists: | pgsql-general |
On 25/11/14 22:24, David G Johnston wrote:
Thanks List, I think this is the right way to go.
> Adrian Klaver-4 wrote
>>> If I am only interested in get 2 entries per result set, I would expect
>>> to see
>> Actually <=2.
>> How do you determine which rows to keep, by id or something else?
>>
>>> 1 xx,yy
>>> 2 xx,yy
>>>
>>>
>>> 1,dd,zz
>>> 2,dd,zz
>>>
>>> 1, ee,ff
>>>
>>> Using LIMIT only gives
>>> 1 xx,yy
>>> 2 xx,yy
>>>
>>> Sorry for not explaining it very, I want to limit the size of an
>>> inviduail set of records which is part of set of records.
>> It would help if we could see the actual query you are using to get the
>> result sets, suitably anonymized if needed.
> The general answer is that you use a window clause and a row_number()
> function over an appropriate partiton. Put that in a subquery then in the
> outer query add a where clause for row_number <= 2.
>
> David J.
>
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> --
> View this message in context: http://postgresql.nabble.com/returning-only-part-of-a-rule-set-tp5828217p5828226.html
> Sent from the PostgreSQL - general mailing list archive at Nabble.com.
>
>
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