使用UNION创建VIEW时插入UNIQUE DUMMY COLUMN

Question

我有一个具有这种结构的表：

我使用此脚本查询请求：

SELECT   D.DELIVERY_REQUEST_ID AS "REQUEST_ID",
         'Delivery' AS "REQUEST_TYPE"
   FROM  DELIVERY_REQUEST D
UNION
SELECT   I.INVOICE_REQUEST_ID AS "REQUEST_ID",
         'Invoice' AS "REQUEST_TYPE"
   FROM  INVOICE_TRX I

结果如下：

    REQUEST_ID    |    REQUEST_TYPE
__________________|____________________
                  |
    1             |    Delivery
    1             |    Invoice
    2             |    Delivery
    2             |    Invoice

我想要做的是在开头用一个唯一的键（应该是一个INT，就像一个自动号码）来查询（或创建一个视图），如下所示：

ID  |  REQUEST_ID    |    REQUEST_TYPE
____|________________|____________________
    |                |
1   |  1             |    Delivery
2   |  1             |    Invoice
3   |  2             |    Delivery
4   |  2             |    Invoice

提前谢谢。

Answer 1

首先，当您添加字符串时使用UNION ALL，因此Oracle不会尝试进行不同的排序。

要实际回答问题，您可以使用分析函数ROW_NUMBER()

select row_number() over ( order by request_id, request_type ) as id
     , a.*
  from ( select d.delivery_request_id as request_id
              , 'delivery' as request_type
           from delivery_request d
          union all
         select i.invoice_request_id as request_id
              , 'invoice' as request_type
           from invoice_trx i
                ) a

Answer 2

为什么你不尝试连续REQUEST_TYPE + REQUEST_ID然后将其放在ID列而不是生成ID？

ID  |  REQUEST_ID    |    REQUEST_TYPE
____|________________|____________________
    |                |
D1  |  1             |    Delivery
I1  |  1             |    Invoice
D2  |  2             |    Delivery
I2  |  2             |    Invoice

Answer 3

你可以使用rownum：

select rownum, REQUEST_ID, REQUEST_TYPE
from
(
SELECT   D.DELIVERY_REQUEST_ID AS "REQUEST_ID",
         'Delivery' AS "REQUEST_TYPE"
   FROM  DELIVERY_REQUEST D
UNION
SELECT   I.INVOICE_REQUEST_ID AS "REQUEST_ID",
         'Invoice' AS "REQUEST_TYPE"
   FROM  INVOICE_TRX I
)

Answer 4

我会说序列是最简单的方法。 如果您希望ID始终从1开始，请在查询之前重新启动序列：

ALTER SEQUENCE temp_id RESTART 1;

不知道这有多快，削减是否有更快的方法。在扩展标准SQL时，某些SQL系统也可能具有此特殊功能。