我面临以下挑战。我需要在同一列上旋转表数据两次。 这是数据截图。
我希望每个项目 ID 各占一行,其中包含每年的购买价值和销售价值。 我尝试通过选择“年份”列两次,对其进行一些格式化,以便每个销售年份都以“S”为前缀,每个购买年份以“P”开头,并使用 2 个枢轴围绕 2 年列旋转。这是 SQL 查询(在 SQL Server 2008 中使用):
SELECT [Item ID],
[P2000],[P2001],[P2002],[P2003],
[S2000],[S2001],[S2002],[S2003]
FROM
(
SELECT [Item ID]
,'P' + [Year] AS YearOfPurchase
,'S' + [Year] AS YearOfSelling
,[Purchasing value]
,[Selling value]
FROM [ItemPrices]
) AS ALIAS
PIVOT
(
MIN ([Purchasing value]) FOR [YearOfPurchase] in ([P2000],[P2001],[P2002],[P2003])
)
AS pvt
PIVOT
(
MIN ([Selling value]) FOR [YearOfSelling] in ([S2000],[S2001],[S2002],[S2003])
)
AS pvt2
结果并不完全是我所希望的(见下图):
如您所见,每个项目 ID 仍然有多于一行。有没有办法将行数减少到每个项目只有一个行数?这样看起来有点像下面的 Excel 截图?
我的建议是应用
UNPIVOT
和 PIVOT
函数来获得结果。
UNPIVOT
会将 PurchasingValue
和 SellingValue
列变成行。完成此操作后,您就可以将数据转换为结果。
代码为:
select *
from
(
select itemid,
case
when col = 'PurchasingValue' then 'P'
when col = 'SellingValue' then 'S'
end + cast(year as varchar(4)) new_col,
value
from yourtable
unpivot
(
value
for col in ([PurchasingValue], [SellingValue])
) unpiv
) src
pivot
(
max(value)
for new_col in (P2000, P2001, P2002, P2003,
S2000, S2001, S2002, S2003)
) piv;
请参阅SQL Fiddle with Demo。结果是:
| ITEMID | P2000 | P2001 | P2002 | P2003 | S2000 | S2001 | S2002 | S2003 |
--------------------------------------------------------------------------
| 1 | 1000 | 1100 | 1200 | 1300 | 900 | 990 | 1080 | 1170 |
| 2 | 500 | 550 | 600 | 650 | 450 | 495 | 540 | 585 |
在 SQL Server 2008+ 中,您可以将
CROSS APPLY
与 VALUES
以及 PIVOT
函数一起使用:
select *
from
(
select itemid,
col+cast(year as varchar(4)) new_col,
value
from yourtable
cross apply
(
VALUES
(PurchasingValue, 'P'),
(SellingValue, 'S')
) x (value, col)
) src
pivot
(
max(value)
for new_col in (P2000, P2001, P2002, P2003,
S2000, S2001, S2002, S2003)
) piv
旋转多个列的一种简单方法是仅使用聚合(Case)表达式。
SELECT [Item ID],
[P2000] = SUM(CASE WHEN [Year] = 2000 THEN [Purchasing value] END),
[P2001] = SUM(CASE WHEN [Year] = 2001 THEN [Purchasing value] END),
[P2002] = SUM(CASE WHEN [Year] = 2002 THEN [Purchasing value] END),
[P2003] = SUM(CASE WHEN [Year] = 2003 THEN [Purchasing value] END),
[S2000] = SUM(CASE WHEN [Year] = 2000 THEN [Selling value] END),
[S2001] = SUM(CASE WHEN [Year] = 2001 THEN [Selling value] END),
[S2002] = SUM(CASE WHEN [Year] = 2002 THEN [Selling value] END),
[S2003] = SUM(CASE WHEN [Year] = 2003 THEN [Selling value] END)
FROM ItemPrices
GROUP BY [Item ID]
使用 GROUP BY ItemID,并对每个结果列使用聚合函数 SUM(isnull(value,0))。
我通过旋转已经旋转的数据集(基本上旋转两次)实现了类似的效果,然后按必要的属性进行分组以获得我之后的结果。仍然可以在几秒钟内执行数千行。