分組LIMIT 10在PostgreSQL

Question

我有一個查詢：

select 
    a.kli, 
    b.term_desc, 
    count(distinct(a.adic)) as count, 
    a.partner_id 

from 
    ad_delivery.sgmt_kli_adic a 
    join wand.wandterms b on a.kli = b.term_code 
    join wand.wandterms c on b.term_desc=c.term_desc 
    join dwh.sgmt_clients e on a.partner_id::varchar = e.partner_id 
    join dwh.schema_names f on e.partner_id::integer = f.partner_id::integer 
where 
    a.partner_id::integer in (f.partner_id) 
    and c.class_code = 969 
group by a.partner_id, b.term_desc, a.kli 
order by partner_id, count desc; 

其帶回每PARTNER_ID某些條款計數。我希望能夠通過計數遞減到顯示前10個每個〜40 PARTNER_ID，以便

查詢結果看起來像

db=# SELECT * FROM xxx; 
pid | term_desc | count 
----+------------+------ 
    4 | termdesc1 | 3434 
    4 | termdesc2 | 235 
    4 | termdesc3 | 367 
    4 | termdesc4 | 4533 
    5 | termdesc1 | 235 
    5 | termdesc2 | 567 
    5 | termdesc3 | 344 
    5 | termdesc4 | 56 
(10k+ rows) 

Answer 1

你可以添加一個排名列，然後過濾結果由排名：

select 
    a.kli, 
    b.term_desc, 
    count(distinct(a.adic)) as count, 
    a.partner_id, 
    RANK() OVER (PARTITION BY a.partner_id order by a.partner_id DESC) AS r 
from 
    ad_delivery.sgmt_kli_adic a 
    join wand.wandterms b on a.kli = b.term_code 
    join wand.wandterms c on b.term_desc=c.term_desc 
    join dwh.sgmt_clients e on a.partner_id::varchar = e.partner_id 
    join dwh.schema_names f on e.partner_id::integer = f.partner_id::integer 
where 
    a.partner_id::integer in (f.partner_id) 
    and c.class_code = 969 
group by a.partner_id, b.term_desc, a.kli 
HAVING r < 11 
order by partner_id, count desc; 

我沒有測試的代碼，但訣竅是排名GROUP BY的每一行和過濾與HAVING子句中的結果，只保留項目比11低等級（你會每組獲得10個項目）。