Question

我正在使用MS SQL Server 2005。

我认为PIVOT可以帮助我，但我无法理解。我一定是在思考。这是输入

create table #myrows (id char(1), seq_i int, val char(10))

insert into #myrows values('A',1, 'A1') 
insert into #myrows values('A',2, 'A2') 
insert into #myrows values('A',3, 'A3') 
insert into #myrows values('A',4, 'A4') 
insert into #myrows values('A',5, 'A5') 
insert into #myrows values('A',6, 'A6') 
insert into #myrows values('A',7, 'A7') 
insert into #myrows values('A',8, 'A8') 
insert into #myrows values('A',9, 'A9') 
insert into #myrows values('A',10, 'A10') 

insert into #myrows values('B',1, 'B1') 
insert into #myrows values('B',2, 'B2') 
insert into #myrows values('B',3, 'B3') 
insert into #myrows values('B',4, 'B4') 
insert into #myrows values('B',5, 'B5') 
insert into #myrows values('B',6, 'B6') 

insert into #myrows values('C',1, 'C1') 
insert into #myrows values('C',2, 'C2') 
insert into #myrows values('C',3, 'C3')

当我传递id时，我可以用T-SQL做到这一点。但我似乎有一个简单的sql视图，我可以创建，不需要我发送它的ID。下面是T-SQL，它为我提供了一个id所需的输出：

DECLARE @max_hierarchy int
DECLARE @code CHAR(1)

select @code = 'C'

SELECT  @max_hierarchy = max(seq_i)
FROM #myrows
WHERE id=@code

SELECT top 1
(SELECT val from #myrows WHERE id=@code AND seq_i = @max_hierarchy) AS 'Level1',
(SELECT val from #myrows WHERE id=@code AND seq_i = @max_hierarchy-1) AS 'Level2',
(SELECT val from #myrows WHERE id=@code AND seq_i = @max_hierarchy-2) AS 'Level3',
(SELECT val from #myrows WHERE id=@code AND seq_i = @max_hierarchy-3) AS 'Level4',
(SELECT val from #myrows WHERE id=@code AND seq_i = @max_hierarchy-4) AS 'Level5'
from #myrows
WHERE id=@code

理想情况下，这将是我正在寻找的SQL输出：

Code Level1      Level2      Level3      Level4      Level5
---- ----------- ----------- ----------- ----------- -----------
A    A10         A9          A8          A7          A6
B    B6          B5          B4          B3          B2
C    C3          C2          C1          NULL        NULL

Answer 1

由于您只想要前5个级别，因此您不需要任何动态旋转，这应该有效：

with cte as (
select id, seq_i, val, ROW_NUMBER() over (partition by id order by seq_i desc) rn
from #myrows
)
select 
  id,
  max(case rn when 1 then val else null end) Level1,
  max(case rn when 2 then val else null end) Level2,
  max(case rn when 3 then val else null end) Level3,
  max(case rn when 4 then val else null end) Level4,
  max(case rn when 5 then val else null end) Level5
from cte
group by id

<强>更新

现在，如果你想让事情更加有趣并动态地设置你的关卡，那么这里有一个不那么琐碎但很有趣的编码解决方案：

create table #cte (id char(1), seq_i int, val char(10), level varchar(10))

;with cte as (
select id, seq_i, val, ROW_NUMBER() over (partition by id order by seq_i desc) rn
from #myrows
)
insert into #cte (id, seq_i, val, level)
select id, seq_i, val, 
       'Level' + right('000' + cast(rn as varchar), 4) from cte 

DECLARE @cols VARCHAR(1000)
DECLARE @sqlquery VARCHAR(2000)

SELECT  @cols = STUFF(( SELECT distinct  ',' + QuoteName(level)
                        FROM #cte FOR XML PATH('')  ), 1, 1, '') 

select @cols 

SET @sqlquery = 'SELECT * FROM
      (SELECT id, level, val
       FROM #cte ) base
       PIVOT (max(val) FOR [level]
       IN (' + @cols + ')) AS finalpivot'

EXECUTE ( @sqlquery )

Answer 2

根据PIVOT运算符

尝试此解决方案

;WITH PivotSource
AS
(
SELECT   a.id
        ,a.seq_i
        ,ROW_NUMBER() OVER(PARTITION BY a.id ORDER by a.seq_i DESC) row_num
FROM    #myrows a
)
SELECT   pvt.id                                 AS Code
        ,pvt.id + CONVERT(VARCHAR(10), pvt.[1]) AS Level1
        ,pvt.id + CONVERT(VARCHAR(10), pvt.[2]) AS Level2
        ,pvt.id + CONVERT(VARCHAR(10), pvt.[3]) AS Level3
        ,pvt.id + CONVERT(VARCHAR(10), pvt.[4]) AS Level4
        ,pvt.id + CONVERT(VARCHAR(10), pvt.[5]) AS Level5                               
FROM    PivotSource src
PIVOT   ( MAX(src.seq_i) FOR src.row_num IN([1], [2], [3], [4], [5]) ) pvt;

结果：

Code Level1      Level2      Level3      Level4      Level5
---- ----------- ----------- ----------- ----------- -----------
A    A10         A9          A8          A7          A6
B    B6          B5          B4          B3          B2
C    C3          C2          C1          NULL        NULL

尝试将底部5值作为列时，T-SQL将行转换为列？

2 个答案: