如何转置表 SQL

Question

我正在尝试转置表，但我收到消息表明列类型与其他列冲突。 这是解决方案

WITH CTE_Unpivoted as
( select ID, Fields, QuantityValue
from Bikes2 as s
UNPIVOT
(QuantityValue for Fields IN(ProductName, Country, Quantity)
)AS u
)
SELECT Fields, [1],[2],[3],[4],[5],[6],[7]
from CTE_Unpivoted AS u
PIVOT
(SUM(QuantityValue) for ID IN ([1],[2],[3],[4],[5],[6],[7])) AS p

这是数据

CREATE TABLE Bikes2
 (ID INT PRIMARY KEY IDENTITY,
 ProductName VARCHAR(50),
 Country VARCHAR(50),
 Quantity INT);
INSERT INTO Bikes2 VALUES ('Road Bike', 'USA', 128)
INSERT INTO Bikes2 VALUES ('Road Bike', 'Italy', 64)
INSERT INTO Bikes2 VALUES ('Electric Bike', 'USA', 257)
INSERT INTO Bikes2 VALUES ('Electric Bike', 'Italy', 143)
INSERT INTO Bikes2 VALUES ('Children Bicecle', 'USA', 386)
INSERT INTO Bikes2 VALUES ('Children Bicecle', 'Italy', 52)
INSERT INTO Bikes2 VALUES ('Road Bike', 'USA', 35)
SELECT * FROM Bikes2

如何正确地做到这一点？有没有可能让它动态化？ 结果是这样的

Answer 1

这种类型的重新格式化最好在应用层而不是在数据库中完成。以下是两个原因：

• SQL 查询返回固定数量的列，并且您似乎希望表中每行一列。所以你必须硬连线这个号码。
• 每一列都有一个类型，但您的数据有字符串和数字。

也就是说，这是可能的。这是一种方法：

with b as (
      select b.*, row_number() over (order by id) as seqnum
      from bikes2 b
     )
select 'productname',
       max(case when seqnum = 1 then productname end),
       max(case when seqnum = 2 then productname end),
       max(case when seqnum = 3 then productname end),
       max(case when seqnum = 4 then productname end),
       max(case when seqnum = 5 then productname end),
       max(case when seqnum = 6 then productname end),
       max(case when seqnum = 7 then productname end)
from b
union all
select 'country',
       max(case when seqnum = 1 then country end),
       max(case when seqnum = 2 then country end),
       max(case when seqnum = 3 then country end),
       max(case when seqnum = 4 then country end),
       max(case when seqnum = 5 then country end),
       max(case when seqnum = 6 then country end),
       max(case when seqnum = 7 then country end)
from b
union all
select 'quantity',
       max(case when seqnum = 1 then cast(quantity as varchar(255)) end),
       max(case when seqnum = 2 then cast(quantity as varchar(255)) end),
       max(case when seqnum = 3 then cast(quantity as varchar(255)) end),
       max(case when seqnum = 4 then cast(quantity as varchar(255)) end),
       max(case when seqnum = 5 then cast(quantity as varchar(255)) end),
       max(case when seqnum = 6 then cast(quantity as varchar(255)) end),
       max(case when seqnum = 7 then cast(quantity as varchar(255)) end)
from b;

这可以缩短为：

with b as (
      select b.*, row_number() over (order by id) as seqnum
      from bikes2 b
     )
select name,
       max(case when seqnum = 1 then val end),
       max(case when seqnum = 2 then val end),
       max(case when seqnum = 3 then val end),
       max(case when seqnum = 4 then val end),
       max(case when seqnum = 5 then val end),
       max(case when seqnum = 6 then val end),
       max(case when seqnum = 7 then val end)
from b cross apply
     (values (1, 'productname', productname),
             (2, 'country', country),
             (3, 'quantity', convert(varchar(255), quantity))
     ) v(ord, name, val)
group by name, ord
order by ord;

Here 是一个 dbfiddle。