Oracle 11g中的自联接表

Question

假设我有一个像这样的查询产生的表：

+-------+-----+--------------------+-----+--------------------+
|CODE   |CURR |FRONT-END CHARGE    |CCY  |BACK-END CHARGE     |
+-------+-----+--------------------+-----+--------------------+
|002    |AUD  |5.25                |PHP  | 3.75               |
|002    |AUD  |1.75                |USD  | 1.25               |
|002    |BGN  |  14                |PHP  | 8.75               |
|002    |BGN  |   6                |USD  | 3.75               |
|002    |BND  | 9.5                |PHP  |  8.5               |
|002    |BND  |4.25                |USD  |12.75               |
|002    |CAD  |12.5                |USD  | 6.75               |
|002    |INR  |  35                |PHP  |22.75               |
|002    |INR  |  25                |USD  |16.25               |
|002    |YEN  |55.5                |PHP  |16.55               |
|002    |YEN  |77.5                |USD  | 39.2               |
+-------+-----+--------------------+-----+--------------------+

但我希望得到这样的结果：

+-------+-----+--------------------+-----+--------------------+
|CODE   |CURR |FRONT-END CHARGE    |CCY  |BACK-END CHARGE     |
+-------+-----+--------------------+-----+--------------------+
|002    |AUD  |7                   |PHP  | 3.75               |
|002    |     |                    |USD  | 1.25               |
|002    |BGN  |20                  |PHP  | 8.75               |
|002    |     |                    |USD  | 3.75               |
|002    |BND  |13.75               |PHP  |  8.5               |
|002    |     |                    |USD  |12.75               |
|002    |CAD  |12.5                |USD  | 6.75               |
|002    |INR  |60                  |PHP  |22.75               |
|002    |     |                    |USD  |16.25               |
|002    |YEN  |133                 |PHP  |16.55               |
|002    |     |                    |USD  | 39.2               |
+-------+-----+--------------------+-----+--------------------+

请注意，前端费用是每种货币的每笔费用的总和。

我尝试使用coalesce但它在选择时返回相同的表。 我也尝试过自我加入，但每项收费的总和都不同了。 这是在oracle 11g

Answer 1

这种类型的转换通常应该在表示层中完成 - 因为结果实际上不是SQL表：行缺少列值。

但是，您可以使用窗口函数执行此操作：

select code,
       (case when row_number() over (partition by code, curr order by front_end_charge desc) = 1
             then code
        end) as code,
       (case when row_number() over (partition by code, curr order by front_end_charge desc) = 1
             then sum(front_end_charge) over (partition by code, curr)
        end) as front_end_charge,
       ccy, back_end_charge
from t
order by t.code, t.curr, t.front_end_charge desc;

重要的是外部order by匹配row_number()表达式中的order by 。 当order by存在时，SQL查询仅以确定的顺序返回结果。