Question

我有下表，并希望使用sum aggregate在多列上使用pivot。

Category        Station1         Station2         Station3
-------------------------------------------------------------
Category1       5.26             6.25             7.28
Category2       4.22             5.00             6.00
Category3       5.00             4.00             8.00
Category1       4.00             7.00             9.00
Category2       2.00             5.00             8.00

并希望输出

My_Station          Category1           Category2             Category3
------------------------------------------------------------------------
Station1            Sum_of_Cat1         Sum_of_Cat2          Sum_of_Cat3
Station2            Sum_of_Cat1         Sum_of_Cat2          Sum_of_Cat3
Station3            Sum_of_Cat1         Sum_of_Cat2          Sum_of_Cat3

使用单个查询。不使用任何循环

由于

Answer 1

这不完全是一个支点。你可以透视和重新编译。我倾向于只编写SQL来执行此操作：

select station as MyStation,
       sum(case when category = 'Category1' then value else 0 end) as Category1,
       sum(case when category = 'Category2' then value else 0 end) as Category2,
       sum(case when category = 'Category3' then value else 0 end) as Category3
from (select n.station, t.category,
             (case when station = 'Station1' then Station1
                   when station = 'Station2' then Station2
                   when station = 'Station3' then Station3
              end) as value
      from t cross join
           (select 'Station1' as station union all select 'Station2' union all select 'Station3') n
     ) t
group by station;

Answer 2

您可以先取消列station1，station2和station3，然后应用PIVOT功能来获得结果。 unpivot进程将多列数据转换为多行。

有几种方法可用于取消数据，包括UNPIVOT函数，UNION ALL查询或使用CROSS APPLY。您没有指定您正在使用的SQL Server版本，但我使用UNION ALL实现了CROSS APPLY，因此代码为：

select category, my_station, value
from yourtable
cross apply
(
  select 'station1', station1 union all
  select 'station2', station2 union all
  select 'station3', station3
) c (my_station, value);

见SQL Fiddle with Demo。这给出了以下结果：

|  CATEGORY | MY_STATION | VALUE |
| Category1 |   station1 |  5.26 |
| Category1 |   station2 |  6.25 |
| Category1 |   station3 |  7.28 |
| Category2 |   station1 |  4.22 |
| Category2 |   station2 |     5 |

正如您所看到的，多站列现在是行。然后，您可以应用PIVOT函数将category值转换为列：

select my_station, category1, category2, category3
from 
(
  select category, my_station, value
  from yourtable
  cross apply
  (
    select 'station1', station1 union all
    select 'station2', station2 union all
    select 'station3', station3
  ) c (my_station, value)
) d
pivot
(
  sum(value)
  for category in (category1, category2, category3)
) piv;

见SQL Fiddle with Demo。这给出了最终结果：

| MY_STATION | CATEGORY1 | CATEGORY2 | CATEGORY3 |
|   station1 |      9.26 |      6.22 |         5 |
|   station2 |     13.25 |        10 |         4 |
|   station3 |     16.28 |        14 |         8 |

在多列sql server上进行数据透视

2 个答案: