SQL 中的 UNION 时如何连接相同 ID 的字符串字段？

Question

我有以下 SELECT:

(SELECT DISTINCT
   V1.FORPDM_ID AS HVID,
   1 AS IMPORT_STATUS,
   V1.CREATEDAT AS IMPORT_DATE,
   'ok' AS IMPORT_MESSAGE,
   V1.ID AS AT_ID,
   V1.FORPDM_TRANSACTION_ID AS TRANSACTION_ID
 FROM V_VALIDATIONCARRIER V1, V_FORPDM_DAVE_HWDEMAND V2
 WHERE
   V1.FORPDM_ID = V2.HVID AND -- JOIN CONDITION
   ...other conditions...
)

UNION ALL

(SELECT DISTINCT
   V1.FORPDM_ID AS HVID,
   0 AS IMPORT_STATUS,
   V1.CREATEDAT AS IMPORT_DATE,
   'PC_ID is null or not in V_PLANNINGCATEGORY' AS IMPORT_MESSAGE,
   V1.ID AS AT_ID,
   V1.FORPDM_TRANSACTION_ID AS TRANSACTION_ID
 FROM V_VALIDATIONCARRIER V1, V_FORPDM_DAVE_HWDEMAND V2
 WHERE (V1.FORPDM_ID = V2.HVID) AND -- JOIN CONDITION
     ...some error conditions...
)

UNION ALL

(SELECT DISTINCT
   V1.FORPDM_ID AS HVID,
   0 AS IMPORT_STATUS,
   V1.CREATEDAT AS IMPORT_DATE,
   'BAUPHASE is null or not in V_SPEEDSPECIFICMASTERDATA' AS IMPORT_MESSAGE,
   V1.ID AS AT_ID,
   V1.FORPDM_TRANSACTION_ID AS TRANSACTION_ID
 FROM V_VALIDATIONCARRIER V1, V_FORPDM_DAVE_HWDEMAND V2
 WHERE (V1.FORPDM_ID = V2.HVID) AND -- JOIN CONDITION
       ...some other error conditions...
)

在我的数据库中，有些行可以匹配两种错误条件，我想在发生这种情况时将两个 IMPORT_MESSAGE 连接起来，这样我就不会得到具有相同 [=14] 的两行=] 和两个不同的 IMPORT_MESSAGE.
当我在查询中也使用 UNION 时，有没有办法在 Oracle 中实现这一点？

编辑
经过一些测试，它起作用了。只是一个澄清：为了让我的所有数据和我应该 select 的消息如下所示：

SELECT DISTINCT HVID, IMPORT_STATUS, IMPORT_DATE, TRANSACTION_ID, AT_ID, LISTAGG(IMPORT_MESSAGE, ',') 
   WITHIN GROUP (ORDER BY IMPORT_MESSAGE) AS 
      IMPORT_MESSAGE FROM ( ...my union all select... ) MYUNION 
   GROUP BY HVID, IMPORT_STATUS, IMPORT_DATE, TRANSACTION_ID, AT_ID;

Answer 1

我认为您必须在 Oracle 环境中使用 LISTAGG 功能。

例如（参见：http://www.sqlines.com/mysql/functions/group_concat）：

SELECT LISTAGG(IMPORT_MESSAGE, ',') WITHIN GROUP (ORDER BY NULL)
FROM (
    .... your union all select
     ) as YOURUNION
GROUP BY YOURUNION.IMPORT_MESSAGE;

我没有Oracle数据库，所以你得试试。

SQL 中的 UNION 时如何连接相同 ID 的字符串字段？

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