Question

大家好日子。我一直无法提出解决方案，正在寻求任何帮助。我有一个表格，我想添加一个列：

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**'

以下是我希望新专栏“Group”的样子：

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

如果Activity_Log是LIKE'％xx％'，我想用字符串添加这个组列，并且在基于ID和Time_Stamp之后的每一行中添加。某些ID在activity_log中不具有该语言，并且Group列对于所有行都将为NULL。对于那些，我想在activity_log是LIKE'％transfer to Group x％'时开始，并在activity_log像'％Transfer to Group x％'或'％ticket was resolved％'时结束。我试图使用OVER（分区依据）来编写一个查询，但是我没有成功。

由于

Answer 1

您可以使用“累积最大值”功能执行此操作。大多数支持窗口函数的数据库都支持此功能，但SQL Server 2012之前的SQL Server除外。

这是方法：

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;

如果您确实想要将其添加为列，则需要更改表以添加列，然后使用update语句。

如果您的数据库不支持累积总和，您仍然可以使用相关子查询来完成工作：

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;

Answer 2

我会使用Gordon Linoff's解决方案，但如果您想要存储ALTER TABLE，可以添加所需的列，如果您只想显示信息{{1}也很好。

SELECT

SQL - 如何基于表中的多个列添加列

2 个答案: