sql - Oracle SQL -- 一个组上的分析函数？

Question

我的表:

ID   NUM   VAL
1    1     Hello
1    2     Goodbye
2    2     Hey
2    4     What's up?
3    5     See you

如果我想返回每个 ID 的最大数量，它真的很好很干净:

SELECT MAX(NUM) FROM table GROUP BY (ID)

但是如果我想获取与每个 ID 的每个数字的最大值相关联的值怎么办？

为什么我不能这样做:

SELECT MAX(NUM) OVER (ORDER BY NUM) FROM table GROUP BY (ID) 

为什么这是一个错误？我想让这个选择按 ID 分组，而不是为每个窗口单独分区......

编辑:错误是“不是 GROUP BY 表达式”。

Answer 1

您可能可以使用 MAX() KEEP(DENSE_RANK LAST...)功能:

with sample_data as (
  select 1 id, 1 num, 'Hello' val from dual union all
  select 1 id, 2 num, 'Goodbye' val from dual union all
  select 2 id, 2 num, 'Hey' val from dual union all
  select 2 id, 4 num, 'What''s up?' val from dual union all
  select 3 id, 5 num, 'See you' val from dual)
select id, max(num), max(val) keep (dense_rank last order by num)
from sample_data
group by id;