SQL函数类似于xmlagg或listagg

Question

我是SQl的新手，我编写了一个查询来从事件数据库中提取事件报告，其中每个事件的数据根据​​事件槽信息存储在不同的表中。 以下是表格：

EVENT_D

ID     HOST       MESSAGE 
---------- ----------------- 
ID1    server1    Server Down
ID2    server2    File System Issue

EVENT_INFO

ID    RECEIVED_TIME          
---------- -------------
ID1   03-05-2019 12:09PM
ID2   03-06-2019 03:00AM

EVENT_OPERATIONS

ID     EG_TIME               EG_OPERATION 
---------- ------------------------------- 
ID1    03-05-2019 12:10 PM    Blacked Out
ID1    03-05-2019 12:10 PM    Reopened
ID1    03-05-2019 12:13 PM    Ownership Taken
ID1    03-05-2019 12:50 PM    Closed
ID2    03-06-2019 03:05 AM    Rule applied
ID2    03-06-2019 03:06 AM    Ownership Taken
ID2    03-06-2019 03:07 AM    Ticket triggered
ID2    03-06-2019 03:30 AM    Closed

预期产出：

ID     HOST       MESSAGE               RECEIVED_TIME           Operations
---------- ------------------------------------------------------------------------------------------------------------------------------------- 
ID1    server1    Server Down           03-05-2019 12:09PM      Blacked Out 03-05-2019 12:10 PM; Reopened 03-05-2019 12:10 PM; Ownership Taken 03-05-2019 12:13 PM; Closed 03-05-2019 12:50 PM
ID2    server2    File System Issue     03-06-2019 03:00AM      Rule applied 03-06-2019 03:05 AM; Ownership Taken 03-06-2019 03:06 AM; Ticket triggered 03-06-2019 03:07 AM; Closed 03-06-2019 03:30 AM

使用的查询：

  SELECT a.ID          AS Event_ID,
         a.HOST        AS Hostname,
         a.MESSAGE     AS EventMessage,
         b.RECEIVED_TIME AS EventReception,
         LISTAGG (
             c.EG_OPERATION || TO_CHAR (c.EG_TIME, 'YYYY-MM-DD hh12:mi:ss AM'),
             ';')
         WITHIN GROUP (ORDER BY c.EG_TIME) as Operations
    FROM EVENT_D a
         INNER JOIN EVENT_INFO b ON b.ID = a.ID
         INNER JOIN EVENT_OPERATIONS c ON c.ID = a.ID
   WHERE     b.RECEIVED_TIME >= TO_DATE ('2019-03-01', 'YYYY-MM-DD hh24:mi:ss')
         AND b.RECEIVED_TIME < TO_DATE ('2019-03-04', 'YYYY-MM-DD hh24:mi:ss')
GROUP BY a.ID,
         a.HOST,
         a.MESSAGE,
         b.RECEIVED_TIME

问题：

如果在没有listagg / xmlagg函数和groupby表达式的情况下执行查询，则输出中的记录数量将为每天6000左右（在实际情况下）。但由于在上述查询中使用了groupby表达式，因此事件计数中存在未命中匹配。事件按主机，消息和其他插槽分组，这反过来影响计数。在实际案例中，我们获得了大约600条记录，而不是6000条记录。

问题：除了listagg / xmlagg之外还有其他功能可以为我们提供预期格式的输出。

Answer 1

也许你想要LISTAGG()作为窗函数：

SELECT . . .,
       LISTAGG (c.EG_OPERATION || TO_CHAR (c.EG_TIME, 'YYYY-MM-DD hh12:mi:ss AM'),
                ';'
               ) WITHIN GROUP (ORDER BY c.EG_TIME) OVER (PARTITION BY ID, HOST) as Operations

然后你会删除GROUP BY。