有几种方法可以将数据从行转换为列。
由于您使用的是 SQL Server 2008,因此您可以使用 PIVOT 函数。
我建议使用该row_number()
功能来帮助旋转数据。如果您有已知数量的值,则可以对查询进行硬编码:
select user, category1, category2, category3, category4
from
(
select [user], category,
'Category'+cast(row_number() over(partition by [user]
order by [user]) as varchar(3)) rn
from yt
) d
pivot
(
max(category)
for rn in (category1, category2, category3, category4)
) piv;
请参阅SQL Fiddle with Demo。
对于您的情况,您声明您将有未知数量的需要作为列的值。在这种情况下,您将需要使用动态 SQL 来生成要执行的查询字符串:
DECLARE @cols AS NVARCHAR(MAX),
@query AS NVARCHAR(MAX)
select @cols = STUFF((SELECT distinct ',' + QUOTENAME('Category'+cast(row_number() over(partition by [user]
order by [user]) as varchar(3)))
from yt
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set @query = 'SELECT [user],' + @cols + '
from
(
select [user], category,
''Category''+cast(row_number() over(partition by [user]
order by [user]) as varchar(3)) rn
from yt
) d
pivot
(
max(category)
for rn in (' + @cols + ')
) p '
execute(@query)
请参阅SQL Fiddle with Demo。两者都给出结果:
| USER | CATEGORY1 | CATEGORY2 | CATEGORY3 | CATEGORY4 |
----------------------------------------------------------
| Bruce | Laptop | Beer | (null) | (null) |
| Chuck | Cell Phone | (null) | (null) | (null) |
| Jack | Shoes | Tie | Glass | (null) |
| Peggy | Shoe | Skirt | Bat | Cat |