基于一列的蜂巢自加入

Question

我在Hive中有一个表，该数据来自SAP系统。该表的列和数据如下：

+======================================================================+
|document_number | year | cost_centre | vendor_account_number | amount | 
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |                       |  123.5 |
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |      1234567890       |  25.96 |
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |                       |  586   |
+----------------------------------------------------------------------+

如上所示，vendor_account_number列的值仅在1行中存在，我想将其带到所有的行中。

预期输出如下：

+======================================================================+
|document_number | year | cost_centre | vendor_account_number | amount | 
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |      1234567890       |  123.5 |
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |      1234567890       |  25.96 |
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |      1234567890       |  586   |
+----------------------------------------------------------------------+

为了实现这一目标，我在Hive中写下了CTE

with non_blank_account_no as(
  select document_number, vendor_account_number
  from my_table
  where vendor_account_number != ''
)

然后自行离开外部加入如下：

select 
    a.document_number, a.year, 
    a.cost_centre, a.amount,
    b.vendor_account_number
from my_table a
left outer join non_blank_account_no b on a.document_number = b.document_number
where a.document_number = ' '

，但我将获得重复的输出，如下所示

+======================================================================+
|document_number | year | cost_centre | vendor_account_number | amount | 
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |      1234567890       |  123.5 |
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |      1234567890       |  25.96 |
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |      1234567890       |  586   |
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |      1234567890       |  123.5 |
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |      1234567890       |  25.96 |
+----------------------------------------------------------------------+
|       1        | 2016 |     XZ10    |      1234567890       |  586   |
+----------------------------------------------------------------------+

任何人都可以帮助我了解我的蜂巢查询有什么问题？

Answer 1

在许多用例中，自加入可以用windows函数

代替

select  document_number
       ,year
       ,cost_center
       ,max (case when vendor_account_number <> '' then vendor_account_number end) over 
        (
            partition by    document_number
        )                                       as vendor_account_number
       ,amount
from    my_table