需要有关 SQL Server PIVOT 的帮助

Question

我了解 SQL Server 中的 PIVOT 功能，并且在这里阅读了一些其他问题和答案，但我似乎无法掌握它来完成我需要的操作。我正在尝试进行一些计算，结果如下：

TABLE office_settings
column office_id (bigint not null)
column setting_value (NVARCHAR(500) NOT NULL)

office_id    setting_value
--------------------------------------------
4             0.2
4             0.2
4             2
4             3
5             0.2
5             0.2
5             2
5             3

我想使用 PIVOT （假设这是适合该工作的工具）将其转换为这个，基本上是“按”office_id 列“分组”，所以：

office_id    value_1    value_2    value_3   value_4
------------------------------------------------------
    4         0.2         0.2         2         3
    5         0.2         0.2         2         3

我还应该提到，在此过程中我需要将setting_value 列值转换为DECIMAL(4,2) - 以防这对完成它所需的T-SQL 有任何影响。

有任何想法吗？

Answer 1

请尝试以下操作：

select office_id,
[1] as value_1, [2] as value_2, 
[3] as value_3, [4] as value_4
from
(
  select office_id, setting_value,
    row_number() over(partition by office_id order by office_id) rnk
  from office_settings
) d
pivot
(
  max(setting_value)
  for rnk in ([1], [2], [3], [4])
) piv;

或者不使用PIVOT（生成相同的执行计划）：

WITH Numbered AS
(
    SELECT 
        OS.office_id,
        OS.setting_value,
        row_num = ROW_NUMBER() OVER (
            -- Note: non-deterministic
            PARTITION BY OS.office_id 
            ORDER BY OS.office_id)
    FROM dbo.office_settings AS OS
)
SELECT
    N.office_id,
    value_1 = MAX(CASE WHEN N.row_num = 1 THEN N.setting_value ELSE NULL END),
    value_2 = MAX(CASE WHEN N.row_num = 2 THEN N.setting_value ELSE NULL END),
    value_3 = MAX(CASE WHEN N.row_num = 3 THEN N.setting_value ELSE NULL END),
    value_4 = MAX(CASE WHEN N.row_num = 4 THEN N.setting_value ELSE NULL END)
FROM Numbered AS N
GROUP BY
    N.office_id;

使用动态 sql（当数据透视列的数量在搜索窗口内变化时很有用）：

declare @pivcols as varchar(200);

select  @pivcols = stuff((select distinct '],[' + cast(row_number() 
over(partition by office_id order by office_id) as varchar(10))
from office_settings
for xml path('')), 1, 2, '') + ']';

declare @pivquery varchar(500); 

set @pivquery = 'Select office_id, '+   
@pivcols +' 
from   
(select office_id, setting_value, 
 row_number() over(partition by office_id order by office_id) rnk
 from office_settings
) as d
PIVOT
(
max(setting_value)
for rnk in ( '+ @pivcols +' )
) AS pvt ';


EXECUTE(@pivquery);