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Date: Fri, 1 Mar 2019 12:59:11 +0100
From: hubert depesz lubaczewski <depesz@depesz.com>
Sender: depesz@depesz.com
To: "Ila B." <ilaria.battiston@gmail.com>
Cc: pgsql-sql@lists.postgresql.org
Subject: Re: Top 3 values for each group in PGSQL
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On Fri, Mar 01, 2019 at 11:51:24AM +0100, Ila B. wrote:
> 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.

Consider reading
https://www.depesz.com/2012/10/05/getting-top-n-rows-per-group/

Best regards,

depesz