从 4 个不同的列中选择单列？答案

【问题标题】：select into single column from instead 4 different columns?从 4 个不同的列中选择单列？
【发布时间】：2013-12-26 14:33:28
【问题描述】：

我试图在案例陈述中使用 4 个不同的列（Case_Close、Case_Open、Case_Comment、Case_Retrieve）将所有内容放在单个列中，不知道该怎么做。我到现在为止是：

 select report_id,
    user_id,
    action_type,
    action_start,
    action_end ,
    CASE WHEN ACTION_END is null THEN  case ACTION_TYPE when 'CLOSE' then ACTION_START  end  END as Case_Close,
    CASE WHEN ACTION_END is null THEN  case ACTION_TYPE when 'OPEN' then GETDATE() end END as Case_Open,
    CASE WHEN ACTION_END is null THEN  case ACTION_TYPE when 'COMMENT' then GETDATE() end END as Case_Comment,
    CASE WHEN ACTION_END is null THEN  case ACTION_TYPE when 'RETRIEVE' then GETDATE() end END as Case_Retrieve

    from Table1
    order by report_id

看起来像这样：

report_id            user_id     action_type action_start            action_end              Case_Close              Case_Open               Case_Comment            Case_Retrieve
-------------------- ----------- ----------- ----------------------- ----------------------- ----------------------- ----------------------- ----------------------- -----------------------
20122511549-621      621         CLOSE       2012-02-19 10:53:28.000 NULL                    2012-02-19 10:53:28.000 NULL                    NULL                    NULL
20122511549-621      621         OPEN        2012-02-05 11:05:49.000 2012-02-19 10:53:28.000 NULL                    NULL                    NULL                    NULL
20132121098-621      621         OPEN        2013-02-12 10:09:08.807 2013-02-12 11:16:17.167 NULL                    NULL                    NULL                    NULL
20132121098-621      621         COMMENT     2013-02-12 11:16:17.167 NULL                    NULL                    NULL                    2013-12-26 14:55:12.017 NULL
201321814390-621     621         OPEN        2013-02-18 14:39:00.157 NULL                    NULL                    2013-12-26 14:55:12.017 NULL                    NULL
201322010148-707     707         OPEN        2013-02-20 10:01:48.693 2013-10-29 13:22:05.017 NULL                    NULL                    NULL                    NULL
201322010148-707     707         RETRIEVE    2013-10-29 13:22:05.017 NULL                    NULL                    NULL                    NULL                    2013-12-26 14:55:12.017
2013222142012-621    621         OPEN        2013-02-22 14:20:12.327 NULL                    NULL                    2013-12-26 14:55:12.017 NULL                    NULL
2013225102516-707    707         OPEN        2013-02-25 10:25:16.790 2013-02-25 10:47:05.890 NULL                    NULL                    NULL                    NULL
2013225102516-707    707         OPEN        2013-02-04 13:48:38.293 2013-10-28 13:22:09.110 NULL                    NULL                    NULL                    NULL
201324134838-707     707         RETRIEVE    2013-10-28 13:22:09.110 NULL                    NULL                    NULL                    NULL                    2013-12-26 14:55:12.017

我需要的是喜欢这个：

report_id            user_id     action_type action_start            action_end              Column_Action_End      
-------------------- ----------- ----------- ----------------------- ----------------------- -----------------------
20122511549-621      621         CLOSE       2012-02-19 10:53:28.000 NULL                    2012-02-19 10:53:28.000
20122511549-621      621         OPEN        2012-02-05 11:05:49.000 2012-02-19 10:53:28.000 NULL                   
20132121098-621      621         OPEN        2013-02-12 10:09:08.807 2013-02-12 11:16:17.167 NULL                   
20132121098-621      621         COMMENT     2013-02-12 11:16:17.167 NULL                    2013-12-26 14:55:12.017
201321814390-621     621         OPEN        2013-02-18 14:39:00.157 NULL                    2013-12-26 14:55:12.017
201322010148-707     707         OPEN        2013-02-20 10:01:48.693 2013-10-29 13:22:05.017 NULL                   
201322010148-707     707         RETRIEVE    2013-10-29 13:22:05.017 NULL                    2013-12-26 14:55:12.017
2013222142012-621    621         OPEN        2013-02-22 14:20:12.327 NULL                    2013-12-26 14:55:12.017
2013225102516-707    707         OPEN        2013-02-25 10:25:16.790 2013-02-25 10:47:05.890 NULL                   
2013225102516-707    707         OPEN        2013-02-04 13:48:38.293 2013-10-28 13:22:09.110 NULL                   
201324134838-707     707         RETRIEVE    2013-10-28 13:22:09.110 NULL                    2013-12-26 14:55:12.017

如果有人可以帮助我，我将不胜感激？

【问题讨论】：

您是否尝试在“action_end”为空时填写？您可以在同一列中执行此操作...使用 coalesce 或 isnull。
谢谢你们所有的人，我尝试了你们所有的答案并为我工作:)

标签： sql-server select case multiple-columns

【解决方案1】：

select report_id,
    user_id,
    action_type,
    action_start,
    action_end ,
    CASE 
        WHEN ACTION_END is null AND ACTION_TYPE = 'CLOSE' then ACTION_START
        WHEN ACTION_END is null AND ACTION_TYPE IN ('OPEN', 'COMMENT', 'RETRIEVE') then GETDATE()
        ELSE NULL 
    END as Column_Action_End

from Table1
order by report_id

【讨论】：

【解决方案2】：

您可以将 case 语句合并为一个，并在每个 WHEN 子句中包含两个条件：

SELECT 
    report_id,
    user_id,
    action_type,
    action_start,
    action_end,
    CASE 
        WHEN ACTION_END is null and ACTION_TYPE = 'CLOSE' then ACTION_START 
        WHEN ACTION_END is null and ACTION_TYPE = 'OPEN' then GETDATE()
        WHEN ACTION_END is null and ACTION_TYPE = 'COMMENT' then GETDATE()
        WHEN ACTION_END is null and ACTION_TYPE = 'RETRIEVE' then GETDATE()
    END as Column_Action_End
FROM Table1
ORDER BY report_id

【讨论】：

【解决方案3】：

您可以使用嵌套的 case 表达式：

Select report_id, user_id, action_type, action_start, action_end ,
    Case When ACTION_END is null
         Then Case When ACTION_TYPE = 'CLOSE' Then ACTION_START
                   When ACTION_TYPE IN ('OPEN','COMMENT', 'RETRIEVE') Then GETDATE() 
              --Else ... (if you need else part for sub case expression) 
              End
    --Else ...(if you need else part for main Case expression)
    End As Column_Action_End
From Table1
Order by report_id

【讨论】：

【解决方案4】：

您可以合并以检查 action_end 是否为空。

如果只有 4 种操作类型并且不是可为空的列，那么您只需检查“CLOSE”...

select report_id,
    user_id,
    action_type,
    action_start,
    coalesce(action_end,case when ACTION_TYPE = 'CLOSE' then ACTION_START else getdate() end) as action_end
from Table1

否则，您必须检查所有 4 个...

select report_id,
    user_id,
    action_type,
    action_start,
    coalesce(action_end,case when ACTION_TYPE = 'CLOSE' then ACTION_START when ACTION_TYPE in ('OPEN','COMMENT','RETRIEVE') then getdate() end) as action_end
from Table1

【讨论】：

谢谢 sam yi，这对我有更多帮助