sql - 如何制作动态栏

Question

我有一些数据如下

Declare @t table (Id int identity,CommaSeperatedValue varchar(100))
Insert Into @t 
Select 'Somalia,Vietnam' Union All 
Select 'apple,banana,guava,India,Australia'

CommaSeperated 值没有限制。所提供示例的所需输出将是

Id  Col1    Col2    Col3    Col4    Col5
1   Somalia Vietnam Null    Null    Null
2   apple   banana  guava   India   Australia

这意味着，列将动态生成。再举个例子

Declare @t table (Id int identity,CommaSeperatedValue varchar(100))
Insert Into @t 
Select 'Somalia,Vietnam,Honolulu,Spain' Union All 
Select 'apple,banana,guava,India,Australia,Smart,Bus' Union All
Select 'Mango'

期望的输出

Id  Col1    Col2    Col3    Col4    Col5        Col6    Col7    
1   Somalia Vietnam Honolulu Spain  Null        Null    Null
2   apple   banana  guava   India   Australia   Smart   Bus
3   Mango   Null    Null    Null    Null        Null    Null

如何做这个查询？

到目前为止我的尝试(在此之后我迷路了)

SELECT 
    X.id,
    X.CommaSeperatedValue,
    Y.splitdata 
FROM
 (
    SELECT *,
    CAST('<X>'+REPLACE(F.CommaSeperatedValue,',','</X><X>')+'</X>' AS XML) AS xmlfilter 
    FROM @t F
 )X
 CROSS APPLY
 ( 
    SELECT fdata.D.value('.','varchar(50)') as splitdata 
    FROM X.xmlfilter.nodes('X') as fdata(D)
 )Y

提前致谢

Answer 1

这是您正在寻找的动态解决方案。我使用了临时表，您可以将其替换为永久表或表变量。

Declare @t table (Id int identity,CommaSeperatedValue varchar(100))
Insert Into @t 
Select 'Somalia,Vietnam' Union All 
Select 'apple,banana,guava,India,Australia'
IF object_ID('TempDB..#Temp') IS NOT NULL DROP TABLE #Temp;
SELECT 
X.id,
--X.CommaSeperatedValue,
Y.splitdata
,ROW_NUMBER() OVER( PARTITION  BY X.id ORDER BY X.id ) AS DataID
INTO #Temp 
FROM
 (
SELECT *,
CAST('<X>'+REPLACE(F.CommaSeperatedValue,',','</X><X>')+'</X>' AS XML) AS xmlfilter 
FROM @t F
 )X
 CROSS APPLY
 ( 
    SELECT fdata.D.value('.','varchar(50)') as splitdata 
    FROM X.xmlfilter.nodes('X') as fdata(D)
 )Y

DECLARE @MAXCol INT = (SELECT MAX(DataID)FROM #Temp)
     ,@index INT =1
     ,@ColNames varchar(4000)=''
     WHILE (@index<=@MAXCol)
     BEGIN 
     SET @ColNames =@ColNames +'MAX(CASE WHEN DataID = '+LTRIM(STR(@index))+' THEN splitdata END) as Col'+LTRIM(STR(@index))+','
     SET @Index=@Index +1        
     END
SET @ColNames = LEFT(@ColNames,LEN(@ColNames)-1) -- Remove Last Comma
EXECUTE   ( 'SELECT
        [id],'+@ColNames+' FROM #Temp GROUP BY [id]'
      )