ランクにアクセスするには

Question

私はPostgreSQLでこのクエリを実行しようとしています。私が望む結果が得られますが、結果を列の値に制限しようとしています。

select eu.* 
from (select count(event), event, u.userid, u.campaign_id, 
      rank() over (partition by u.campaign_id order by count(event) desc) as THISHERE 
     from events e join 
      users u 
      on u.userid = e.userid 
     group by event, 3 , 4 
    ) eu 
where THISHERE = 1 
order by 1 desc 
limit 20; 

私はあなたができると思う： "thishere" あなたはサブクエリを使用する必要が

Answer 1

存在しないカラム：

select count(event), event, u.userid, u.campaign_id, 
rank() over (partition by u.campaign_id order by count(event) desc) as THISHERE 
from events e join users u on u.userid = e.userid 
where THISHERE=1 
group by event, 3 , 4 
order by 1 desc 
limit 20; 

ERROR：しかし、それは私が列にアクセスすることはできません。 distinct onを使用してください：

select distinct on (campaign_id) count(event), event, u.userid, u.campaign_id, 
      rank() over (partition by u.campaign_id order by count(event) desc) as THISHERE 
from events e join 
    users u 
    on u.userid = e.userid 
group by event, 3 , 4 
order by campaign_id, count(event) desc 
fetch first 20 rows only;