1

我有以下 derby sql 语句：

    SELECT DISTINCT MEETINGS.MEETING_ID,
        MEETINGS.TITLE,
        RECORDING_FRAME.STARTTIME,
        RECORDING_FRAME.ENDTIME,
        {
                fn timestampdiff(SQL_TSI_FRAC_SECOND,
                RECORDING_FRAME.STARTTIME,
                RECORDING_FRAME.ENDTIME)
        } AS RUNTIMEFIELD_SESSIONDURATION
FROM APP.MEETINGS
JOIN APP.RECORDING ON
        MEETINGS.MEETING_ID=RECORDING.MEETINGID
JOIN APP.RECORDING_TRACK ON
        RECORDING.RECORDING_ID=RECORDING_TRACK.RECORDING_ID
JOIN APP.RECORDING_FRAME ON
        RECORDING.RECORDING_ID=RECORDING_FRAME.RECORDING_ID
WHERE RECORDING_FRAME.MODULE LIKE 'Recorder' AND
        MEETINGS.STATUS LIKE 'ENDED'

如果我执行这个查询，我会得到以下结果：

MEETING_ID  TITLE                 STARTTIME            ENDTIME              RUNTIMEFIELD_SESSIONDURATION  
----------  --------------------  -------------------  -------------------  ----------------------------  
65536       abc                   2013-03-06 21:28:49  (null)               (null)                        
65536       abc                   (null)               2013-03-06 21:30:04  (null)                        
65537       fasfasf               2013-03-06 21:13:13  (null)               (null)                        
65537       fasfasf               (null)               2013-03-06 21:13:40  (null)                        
360448      fasfffa               2013-03-06 21:31:07  (null)               (null)                        
360448      fasfffa               (null)               2013-03-06 21:38:13  (null)                        
360448      fasfffa               (null)               (null)               (null)                        
360450      test                  2013-03-06 22:07:31  (null)               (null)                        
360450      test                  (null)               2013-03-06 22:14:13  (null)                        
1605632     test benno            2013-03-19 18:21:03  (null)               (null)                        
1605632     test benno            (null)               2013-03-19 18:28:02  (null)                        
1605632     test benno            (null)               (null)               (null)                        
3211281     Conference Unni       2013-03-28 11:03:34  (null)               (null)                        
3211281     Conference Unni       (null)               2013-03-28 11:12:49  (null)                        
3211281     Conference Unni       (null)               (null)               (null)                        
3211283     test                  2013-03-28 10:51:27  (null)               (null)                        
3211283     test                  (null)               2013-03-28 10:59:13  (null)                        
3211283     test                  (null)               (null)               (null)                        
3211284     test (Copy)           2013-03-28 11:02:57  (null)               (null)                        
3211284     test (Copy)           (null)               2013-03-28 11:03:08  (null)                        
3211285     test (Copy) (Kopie)   2013-03-28 18:24:35  (null)               (null)                        
3211285     test (Copy) (Kopie)   (null)               2013-03-28 18:24:58  (null)                        
3211288     ss test               2013-03-28 17:02:20  (null)               (null)                        
3211288     ss test               (null)               2013-03-28 17:34:33  (null)                        
3211288     ss test               (null)               (null)               (null)

现在，很明显，该清单中的同一事件（例如，事件“abc”）有两条记录，开始时间和结束时间。如何修改此 derby sql 语句，使其在单行中返回事件“abc”开始时间和结束时间？

4

2 回答 2

3

而不是DISTINCT使用and ：GROUP BYMAX(start)MAX(end)

您的查询将是这样的：

SELECT id, title, MAX(start), MAX(end)
FROM ....
JOIN...
WHERE ...
GROUP BY id, title

由于聚合函数跳过NULLs 并且每个事件只有 1 个开始和结束MAX，因此会产生正确的结果。

编辑：使用持续时间计算 

SELECT minmax.*, 
        {
          fn timestampdiff(SQL_TSI_FRAC_SECOND,
                minmax.StartTime,
                minmax.EndTime)
        } AS RUNTIMEFIELD_SESSIONDURATION
FROM 
    (SELECT id, title, MAX(start) As StartTime, MAX(end) As EndTime
    FROM ....
    JOIN...
    WHERE ...
    GROUP BY id, title) minmax

来自 Derby 文档的表子查询部分：http: //db.apache.org/derby/docs/10.2/ref/

于 2013-05-12T21:39:16.120 回答
1

在我看来，表 RECORDING_FRAME 似乎有 2 或 3 行与 RECORDING_ID 上的 RECORDING_TRACK 连接。一行的 starttime 不为空，但 endtime 为空，一行的 starttime 为空，但 endtime 不为空，有些录音还有第三行的 starttime 和 endtime 为空。您需要做的是将联合（多行）转换为连接（单行）。这是你如何做到的：

首先创建一个 RECORDING_FRAME 视图，该视图仅包含 starttime 不为空的行。

Create view APP.VW_RF_START as
 (Select RECORDING_ID, STARTTIME from RECORDING_FRAME
  where STARTTIME is not null)

现在创建一个视图，其中仅包含 RECORDING_FRAME 的记录，其中 endtime 不为空。

Create view APP.VW_RF_END as
 (Select RECORDING_ID, STARTTIME from RECORDING_FRAME
  where ENDTIME is not null)

现在，如果您在recording_id 上加入两个视图，您的开始时间和结束时间在同一行。你的查询是：

SELECT DISTINCT 
 MEETINGS.MEETING_ID, MEETINGS.TITLE,
 VW_RF_START.STARTTIME, VW_RF_END.STARTTIME,
 {
            fn timestampdiff(SQL_TSI_FRAC_SECOND,
            RECORDING_FRAME.STARTTIME,
            RECORDING_FRAME.ENDTIME)
 } AS RUNTIMEFIELD_SESSIONDURATION
FROM APP.MEETINGS
JOIN APP.RECORDING ON
    MEETINGS.MEETING_ID=RECORDING.MEETINGID
JOIN APP.RECORDING_TRACK ON
    RECORDING.RECORDING_ID=RECORDING_TRACK.RECORDING_ID
JOIN APP.VW_RF_START ON
    RECORDING.RECORDING_ID=VW_RF_START.RECORDING_ID
JOIN APP.VW_RF_END ON
    RECORDING.RECORDING_ID=VW_RF_START.RECORDING_ID

WHERE RECORDING_FRAME.MODULE LIKE 'Recorder' 和 MEETINGS.STATUS LIKE 'ENDED'

如果您无法创建视图，则可以在查询中定义它们：

SELECT DISTINCT 
 MEETINGS.MEETING_ID, MEETINGS.TITLE,
 VW_RF_START.STARTTIME, VW_RF_END.STARTTIME,
 {
            fn timestampdiff(SQL_TSI_FRAC_SECOND,
            RECORDING_FRAME.STARTTIME,
            RECORDING_FRAME.ENDTIME)
 } AS RUNTIMEFIELD_SESSIONDURATION
FROM APP.MEETINGS
APP.RECORDING ON
    MEETINGS.MEETING_ID=RECORDING.MEETINGID
JOIN APP.RECORDING_TRACK ON
    RECORDING.RECORDING_ID=RECORDING_TRACK.RECORDING_ID
JOIN 
  (Select RECORDING_ID, STARTTIME from RECORDING_FRAME
  where ENDTIME is not null) as VW_RF_START
ON
    RECORDING.RECORDING_ID=VW_RF_START.RECORDING_ID
JOIN 
  (Select RECORDING_ID, STARTTIME from RECORDING_FRAME
  where ENDTIME is not null) as APP.VW_RF_END 
ON RECORDING.RECORDING_ID=VW_RF_START.RECORDING_ID
WHERE RECORDING_FRAME.MODULE LIKE 'Recorder' AND
    MEETINGS.STATUS LIKE 'ENDED'
于 2013-05-12T22:05:25.337 回答