Question

我使用一些CASE语句从活动日志中提取相应的信息。活动日志的要点是工作ID将具有多个活动和日期，这里是简化，即：。

+-----+--------------------------+-------------+
| ID  |         activity         |    date     |
+-----+--------------------------+-------------+
| 123 | assigned                 | 2016-01-05  |
| 123 | escalated                | 2016-01-06  |
| 123 | returned from escalation | 2016-01-07  |
| 123 | escalated                | 2016-01-08  |
| 123 | returned from escalation | 2016-01-09  |
| 123 | completed                | 2016-02-06  |
+-----+--------------------------+-------------+

我使用了多个CASE语句将结果转换成如下：

+-----+------------+------------+------------+
| ID  |  assigned  | escalated  |  returned  |
+-----+------------+------------+------------+
| 123 | 2016-01-05 | NULL       | NULL       |
| 123 | NULL       | 2016-01-06 | NULL       |
| 123 | NULL       | NULL       | 2016-01-07 |
| 123 | NULL       | 2016-01-08 | NULL       |
| 123 | NULL       | NULL       | 2016-01-09 |
+-----+------------+------------+------------+

如何摆脱NULL并将其变成大致类似的东西：

+-----+------------+------------+------------+
| ID  |  assigned  | escalated  |  returned  |
+-----+------------+------------+------------+
| 123 | 2016-01-05 | 2016-01-06 | 2016-01-07 |
| 123 | NULL       | 2016-01-08 | 2016-01-09 |
+-----+------------+------------+------------+

我最接近的是做this人提出的建议。不幸的是，使用MAX或MIN并按ID分组只能给我一个独特的结果。我目前正在尝试将这些案件放在CTE中，但不确定从那里开始。

Answer 1

您可以使用条件聚合与row_number() ：

执行此操作

select t.id,
       max(case when activity = 'assigned' then date end) as assigned,
       max(case when activity = 'escalated' then date end) as escalated,
       max(case when activity = 'returned from escalation ' then date end) as returned
from (select t.*,
             row_number() over (partition by id, activity order by date) as seqnum
      from t
     ) t
group by id, seqnum;

在使用case语句并返回多个结果后删除NULL

1 个答案: