Oracle，使用 order by desc 和 rownum 获取第一行

Question

这个查询给出了无效标识符错误，我知道这是因为子查询将只能访问更高一层的数据。

select *
from   t2_callerid_plan cp
where  cp.subsrefnum in (
       select *
       from   (
              select vsap.subsrefnum
              from   prv_internet_responses_vsap vsap
              where  vsap.subsrefnum = cp.subsrefnum
              order by vsap.id desc
       )
       where rownum = 1
);

现在，我在想是否有办法可以创建查询，在子查询中使用来自查询的数据时，只能 return 最新的行？

Answer 1

你可以试试这个：

  select *
from   t2_callerid_plan cp
inner join
(
 select vsap.subsrefnum,ROW_NUMBER()  OVER (PARTITION BY subsrefnum ORDER BY vsap.id desc) rn
              from   prv_internet_responses_vsap vsap 
)vsap
on    vsap.subsrefnum = cp.subsrefnum and vsap.rn=1

Answer 2

您可以使用 ROW_NUMBER() :

SELECT * FROM ( 
    SELECT cp.*,
           ROW_NUMBER() OVER(PARTITION BY cp.subsrefnum ORDER BY vsap.id desc) as rnk
    from t2_callerid_plan cp
    JOIN  prv_internet_responses_vsap vsap
     ON vsap.subsrefnum = cp.subsrefnum) p
WHERE p.rnk = 1

Oracle，使用 order by desc 和 rownum 获取第一行

Oracle, get top row using order by desc and rownum

sql

oracle

greatest-n-per-group