From: Thomas Kellerer <spam_eater@gmx.net>
To: pgsql-sql@lists.postgresql.org
Subject: Re: Top 3 values for each group in PGSQL
Date: Fri, 1 Mar 2019 13:52:02 +0100
Message-ID: <50d9b39f-56f8-8bc8-a93a-d5feb16f4dd3@gmx.net> (raw)
In-Reply-To: <67FB61BF-CF8F-440E-B4C5-B6F72D61A9C7@gmail.com>
References: <67FB61BF-CF8F-440E-B4C5-B6F72D61A9C7@gmail.com>
Ila B. schrieb am 01.03.2019 um 11:51:
> Hello,
>
> I’m working on a health database and I’m trying to extract the most popular prescription codes from a custom table I structured like this:
>
> Year - Code - Count(code)
>
> I want to extract the 3 codes with maximum count for each year. I know I should be using rank() but I don’t really understand how this works.
> I am using pgAdmin4 version 3.5 with PostgreSQL 10.6 on Windows 10 Pro and no permission to update.
Something along the lines:
select code, year, "count"
from (
select code, year, "count",
dense_rank() over (partition by code, year order by "count" desc) as rnk
from the_table
) t
where rnk <= 3;
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Subject: Re: Top 3 values for each group in PGSQL
In-Reply-To: <50d9b39f-56f8-8bc8-a93a-d5feb16f4dd3@gmx.net>
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