SQL - 如何根据表中的多列添加列

美好的一天每个人。我一直无法提出解决方案并正在寻求任何帮助。我有，我想增加一列的表：SQL - 如何根据表中的多列添加列

ID  Time_Stamp      Activity_Log 
1254 6/1/2013 8:00:00AM   'Ticket was opened by user A' 
1254 6/2/2013 8:20:00AM   'Comment was logged by user B' 
1254 6/4/2013 8:25:00AM   '**Ticket was transferred to Group 1**' 
1254 6/7/2013 8:50:00AM   'Comment was logged by user B' 
1254 6/11/2013 10:00:00AM  'Comment was logged by user C' 
1254 6/12/2013 12:00:00PM  '**Ticket was transferred to Group 2**' 
7589 6/3/2013 11:00:00PM  'Ticket was opened by user A' 
7589 6/5/2013 1:00:00PM   'Comment was logged by user C' 
7589 6/7/2013 2:00:00PM   'Resolution provided by user C' 
7589 6/11/2013 5:00:00PM  'Ticket resolved by user C' 
8526 6/3/2013 7:00:00PM  'Ticket opened by user D' 
8526 6/4/2013 2:00:00PM  '**Ticket was transferred to Group 2**' 
8526 6/5/2013 1:00:00PM  'Comment was logged by user G' 
8526 6/8/2013 5:00:00PM  '**Ticket was resolved by user C**'

这里就是我想新列，组，看起来像：

ID  Time_Stamp      Activity_Log       Group 
1254 6/1/2013 8:00:00AM   'Ticket was opened by user A'    NULL 
1254 6/2/2013 8:20:00AM   'Comment was logged by user B'    NULL 
1254 6/4/2013 8:25:00AM   '**Ticket was transferred to Group 1**'  Group 1 
1254 6/7/2013 8:50:00AM   'Comment was logged by user B'    Group 1 
1254 6/11/2013 10:00:00AM  'Comment was logged by user C'    Group 1 
1254 6/12/2013 12:00:00PM  '**Ticket was transferred to Group 2**'  Group 2 
7589 6/3/2013 11:00:00PM  'Ticket was opened by user A'    NULL 
7589 6/5/2013 1:00:00PM   'Comment was logged by user C'    NULL 
7589 6/7/2013 2:00:00PM   'Resolution provided by user C'    NULL 
7589 6/11/2013 5:00:00PM  'Ticket resolved by user C'     NULL 
8526 6/3/2013 7:00:00PM  'Ticket opened by user D'      NULL 
8526 6/4/2013 2:00:00PM  '**Ticket was transferred to Group 2**'  Group 2 
8526 6/5/2013 1:00:00PM  'Comment was logged by user G'    Group 2 
8526 6/8/2013 5:00:00PM  '**Ticket was resolved by user C**'   Group 2

我想补充这如果Activity_Log是LIKE'％xx％'，并且基于ID和Time_Stamp之后的每一行都包含字符串。某些ID在activity_log中将不具有该语言，并且组列对于所有行都将为NULL。对于那些做的，我希望在activity_log开始时LIKE'％转移到组x％'，并在activity_log类似于'％转移到组x％'或'％ticket was resolved％'时结束。我试图用OVER（partition by）编写一个查询来区分ID，但我没有成功。

谢谢

来源

2013-07-23 user2610646

那么......计算列？另外，哪个DBMS是这样的？ [tag：sql]有点太模棱两可了。附：根据表的大小，您可能只需添加一个普通列，通过一次运行解析器，然后使用触发器来保持新列同步。计算/计算的列在增加的开销方面可能非常密集。 –

应该编写这个“组”列是应用程序代码而不是数据库的责任？看起来应用程序代码具有正确设置所需的所有信息。 –

您可以使用“累计最大值”功能做到这一点。这是由支持窗口函数大多数数据库之前，SQL Server 2012的

这里的支持，与SQL Server的例外是方法：

select t.id, t.Time_Stamp, t.Activity_Log, 
     MAX(GroupName) over (partition by id order by TimeStamp) as "Group"  
from (select t.*, 
      (case when Activity_Log like '%transferred to Group%' 
        then left(RIGHT(Activity_Log, 9), 7) 
       end) as GroupName 
     from t 
    ) t;

如果你真的想添加为一列，您需要更改表格以添加列，然后使用update声明。

如果数据库不支持的累加值，你仍然可以做的工作与相关子查询：

select t.id, t.Time_Stamp, t.Activity_Log, 
     (select left(RIGHT(t2.Activity_Log, 9), 7) 
     from t t2 
     where t2.id = t.id and 
       t2.TimeStamp <= t.TimeStamp and 
       Activity_Log like '%transferred to Group%' 
     order by t2.TimeStamp desc 
     limit 1 
     ) as "Group" 
from t;

来源

2013-07-23 14:14:43

我会Gordon Linoff's解去，但您可以添加您需要的列一个ALTER TABLE如果你想存储它，如果你只想显示信息，那么SELECT也可以。

ALTER TABLE tblLog 
ADD Group VARCHAR(4)

来源

2013-07-23 15:14:50 mike27015

SQL - 如何根据表中的多列添加列

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