SQL服務器查詢通過

Question

給出的以下結構的表：

subscriber_id，帶

11,1

12,1

13,1

...

21,2

22.2

23.2

24.2

...

N1，正

N2，正

N3，正

...

nm，n

我想從每個組中獲得n％大小的用戶子組。對於10％，我應該得到組1的10％，組2的10％...組n的10％。

Answer 1

這聽起來像你想要一個分層樣本。您可以通過在每個組中首先枚舉並隨後選擇所需的「n」個記錄來獲得此信息。這裏是如何做到這一點在SQL Server中的例子：

select t.id, t.band 
from (select t.*, 
      row_number() over (order by band_seqnum) as seqnum 
     from (select t.*, 
        row_number() over (partition by band order by rand(checksum()) as band_seqnum, 
        count(*) over() as cnt 
      from t 
      ) t 
    ) t 
where band_seqnum <= 0.10 * cnt; 

Answer 2

嘗試這個

Select * from 
(
Select *, NTILE(n%) over(partition by id order by id) 'R' from t)t 
where t.R<=(n%)