mysql - 使用sql查询从单列设置两个列值

Question

我有一张包含以下详细信息的表格

ID    statusID  logTime
100238  1   2011-07-07 03:48:43.000
100238  2   2011-07-07 03:48:46.000
100238  1   2011-07-07 09:07:57.000
100238  2   2011-07-07 16:12:28.000
100238  1   2011-07-08 02:59:57.000
100238  2   2011-07-08 03:00:00.000
100238  1   2011-07-08 09:26:37.000
100238  2   2011-07-08 14:03:05.000

所需的输出应该是这样的

repID   ClockIn                    ClockOut
100238  2011-07-07 03:48:43.000    2011-07-07 03:48:46.000
100238  2011-07-07 09:07:57.000    2011-07-07 16:12:28.000
100238  2011-07-08 02:59:57.000    2011-07-08 03:00:00.000
100238  2011-07-08 09:26:37.000    2011-07-08 14:03:05.000

即.. 如果 statusID 为 1，则 logtime 必须在 ClockIn 列中，如果 statusID 为 2，则 logtime 必须在 ClockOut 列中

我用过这样的查询

SELECT repID,
       ClockIn,
       ClockOut from
  (SELECT a.eventID, 
          a.repID, 
          a.logTime, 
          CASE WHEN a.statusID = 1 THEN a.logTime ELSE NULL END AS ClockIn, 
          CASE WHEN b.statusID = 2 THEN b.logTime ELSE NULL END AS ClockOut
   FROM tbl_ets_reptimelog a
   LEFT JOIN tbl_ets_reptimelog b ON a.repID = b.repID)c

结果如下

repID   ClockIn                     ClockOut
100238  2011-07-07 03:48:43.000     NULL
100238  2011-07-07 03:48:43.000     2011-07-07 03:48:46.000
100238  2011-07-07 09:07:57.000     NULL
100238  2011-07-07 09:07:57.000     2011-07-07 16:12:28.000
100238  2011-07-08 02:59:57.000     NULL
100238  2011-07-08 02:59:57.000     2011-07-08 03:00:00.000
100238  2011-07-08 09:26:37.000     NULL
100238  2011-07-08 09:26:37.000     2011-07-08 14:03:05.000

如何删除 ClockOut 列中出现的带有 NULL 值的额外行

请帮忙解决这个问题......

Answer 1

只需在外部查询中添加一个 WHERE 子句

select repID,ClockIn,ClockOut from(select a.eventID, a.repID, a.logTime, 
case when a.statusID = 1 then a.logTime else null end as ClockIn,  
case when b.statusID = 2 then b.logTime else null end as ClockOut from tbl_ets_reptimelog a 
left join tbl_ets_reptimelog b on a.repID = b.repID)c
WHERE ClockOut IS NOT NULL