Re: Top 3 values for each group in PGSQL - Mailing list pgsql-sql

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
structuredlike 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
understandhow 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;