Re: Selecting top N percent of records.
От
Tim Uckun
Тема
Re: Selecting top N percent of records.
Дата
Msg-id
AANLkTimBXwCheGaet+qKdZ_xGJxOUe4zs6KMRMBYeEps@mail.gmail.com
Ответ на
Re: Selecting top N percent of records. (Peter Geoghegan)
Список
Дерево обсуждения
Selecting top N percent of records. Tim Uckun <timuckun@gmail.com>
Re: Selecting top N percent of records. Darren Duncan <darren@darrenduncan.net>
Re: Selecting top N percent of records. Tim Uckun <timuckun@gmail.com>
Re: Selecting top N percent of records. Peter Geoghegan <peter.geoghegan86@gmail.com>
Re: Selecting top N percent of records. Tim Uckun <timuckun@gmail.com>
Re: Selecting top N percent of records. Craig Ringer <craig@postnewspapers.com.au>
Re: Selecting top N percent of records. Tim Uckun <timuckun@gmail.com>
> That is a bit problematic because it necessitates knowing the number > of rows total, and slow counting is an idiosyncrasy of postgres. > > http://wiki.postgresql.org/wiki/Slow_Counting > > To get the top 10%: > > SELECT * FROM table LIMIT(SELECT (COUNT(*) * 0.1)::integer FROM table) I think I wasn't making myself clear. I don't want the top 10% of the rows. I want the rows with the top 10% of the values in a column. In my case there is a very non linear set of values. The lowest value is 1 and the vast majority of records have a 1 in the column. The highest value might be in the tens of thousands. I want to pull up the records that have the top ten percent values.
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