c# - 从 SQL 中的一列创建类别列名

Question

我有看起来像这样的 oracle 表：

ID---Date------------Type
1  |  01/01/2013  | Install Date 
1  |  05/01/2013  | Complete Date 
1  |  10/01/2013  | Closed Date
2  |  02/01/2013  | Install Date
2  |  03/02/2013  | Closed Date
3  |  10/01/2013  | Install Date
3  |  13/01/2013  | Closed Date
4  |  07/01/2013  | Install Date
4  |  09/01/2013  | Complete Date
4  |  17/01/2013  | Closed Date

我想要实现的是查询它以获得这样的结果：

ID--InstallDate--CompleteDate--ClosedDate------
1 | 01/01/2013 | 05/01/2013 | 10/01/2013 
2 | 02/01/2013 | --null-----| 03/02/2013
3 | 10/01/2013 | --null-----| 13/01/2013
4 | 07/01/2013 | 09/01/2013 | 17/01/2013

Answer 1

这将做：

SELECT  ID,
        MAX(CASE WHEN Type = 'Install Date' THEN Date END) InstallDate,
        MAX(CASE WHEN Type = 'Complete Date' THEN Date END) CompleteDate,
        MAX(CASE WHEN Type = 'Closed Date' THEN Date END) ClosedDate
FROM OracleTable
GROUP BY ID
ORDER BY ID

Answer 2

这是一个相对标准的数据透视查询（尽管需要进行数据透视表明数据模型存在根本问题）。老式的方法是做类似的事情

SELECT id,
       MAX( CASE WHEN type = 'Install Date' THEN dt ELSE null END ) install_date,
       MAX( CASE WHEN type = 'Complete Date' THEN dt ELSE null END ) complete_date,
       MAX( CASE WHEN type = 'Closed Date' THEN dt ELSE null END ) closed_date
  FROM your_table_name
 GROUP BY id

由于您使用的是 11g，因此您还可以使用PIVOT运算符

select *
  from (select id, dt, type 
          from your_table_name)
 pivot (max(dt) as dt FOR (type) in ('Install Date' as install, 
                                     'Complete Date' as complete, 
                                     'Closed Date' as closed))