Re: how to get row number in select query

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От Thomas Kellerer
Тема Re: how to get row number in select query
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Msg-id ihs31q$1lm$1@dough.gmane.org
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Ответ на Re: how to get row number in select query  (Piotr Czekalski <pczekalski@techbaza.pl>)
Ответы Re: how to get row number in select query  (Emi Lu <emilu@encs.concordia.ca>)
Список pgsql-sql
Piotr Czekalski, 27.01.2011 16:21:
> Gentelmen,
>
> I follow this thread and I don't exactly get an idea of yours, but
> isn't is as simple as (example: table "web.files" contains one column
> named "fileurl" ):
>
> select row_number() over(), X.fileurl from (select fileurl from
> web.files order by fileurl) X
>
> The only disadvantage is that if you do want to order resultset you
> have to use "select from select" as numbers are added before order
> which may cause some performance troubles.
>

You can get the row_number() without using the sub-select and without ordering the whole result as you can specify the
orderin the over() clause:
 

select fileurl       row_number() over (order by fileurl)
from web.files

Regards
Thomas



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