从每组中选择前15条记录

我想选择10个商户账户，为每个商户账户挑选前15条交易记录，页面大小如10*50？

我有这个查询，它给我提供了最多的记录，我需要修复来选择"每个商家帐户ID的前15条记录"，而不仅仅是前150条记录。

欢迎任何指针、建议、代码修复！

SELECT * FROM (
             SELECT account_id,transaction_id,ROWNUM RNUM
             FROM transactions 
             WHERE status='P' AND ROWNUM < ( (p_page_number * p_page_size) + 1)
             GROUP BY account_id,transaction_id, ROWNUM
             ORDER BY account_id                 
             ) a
      WHERE rnum >= ( ( (p_page_number - 1) * p_page_size) + 1);

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解决方案

您可以使用DENSE_RANK()窗口函数将组号分配给行，并使用ROW_NUMBER()在每个组中分配序列号。然后，过滤就很容易了。

例如：

select *
from (
  select
    account_id, 
    transaction_id,
    dense_rank() over(order by account_id) as g,
    row_number() over(partition by account_id order by transaction_id) as rn
  from transactions
  where status = 'P'
) x
where g <= 10 -- the first 10 groups (accounts)
  and rn <= 15 -- the first 15 transactions within each group