T-SQL - 将逗号分隔的列转换为多列

Question

从下表中，如何将Values列转换为多列，并填充单独的值，这些值当前由逗号分隔？在转换前：

Name Values 
---- ------ 
John val,val2,val3 
Peter val5,val7,val9,val14 
Lesli val8,val34,val36,val65,val71,val 
Amy val3,val5,val99 

转换的结果应该是这样的：

Name Col1 Col2 Col3 Col4 Col5 Col6 
---- ---- ---- ---- ---- ---- ---- 
John val val2 val3 
Peter val5 val7 val9 val14 
Lesli val8 val34 val36 val65 val71 val 
Amy val3 val5 val99 

Answer 1

首先，你使用的是什么数据库产品和版本？如果您在使用SQL Server 2005及更高版本，你可以写一个分离的用户定义函数，像这样：

CREATE FUNCTION [dbo].[Split] 
( 
    @DelimitedList nvarchar(max) 
    , @Delimiter varchar(2) = ',' 
) 
RETURNS TABLE 
AS 
RETURN 
    (
    With CorrectedList As 
     (
     Select Case When Left(@DelimitedList, DataLength(@Delimiter)) <> @Delimiter Then @Delimiter Else '' End 
      + @DelimitedList 
      + Case When Right(@DelimitedList, DataLength(@Delimiter)) <> @Delimiter Then @Delimiter Else '' End 
      As List 
      , DataLength(@Delimiter) As DelimiterLen 
     ) 
     , Numbers As 
     (
     Select TOP (Coalesce(Len(@DelimitedList),1)) Row_Number() Over (Order By c1.object_id) As Value 
     From sys.objects As c1 
      Cross Join sys.columns As c2 
     ) 
    Select CharIndex(@Delimiter, CL.list, N.Value) + CL.DelimiterLen As Position 
     , Substring (
        CL.List 
        , CharIndex(@Delimiter, CL.list, N.Value) + CL.DelimiterLen  
        , CharIndex(@Delimiter, CL.list, N.Value + 1)       
         - (CharIndex(@Delimiter, CL.list, N.Value) + CL.DelimiterLen) 
        ) As Value 
    From CorrectedList As CL 
     Cross Join Numbers As N 
    Where N.Value < Len(CL.List) 
     And Substring(CL.List, N.Value, CL.DelimiterLen) = @Delimiter 
    ) 

然后可以打出值你想用一个类似于：

Select Name, Values 
From Table1 As T1 
Where Exists (
       Select 1 
       From Table2 As T2 
        Cross Apply dbo.Split (T1.Values, ',') As T1Values 
        Cross Apply dbo.Split (T2.Values, ',') As T2Values 
       Where T2.Values.Value = T1Values.Value 
        And T1.Name = T2.Name 
       ) 

Answer 2

这是一个解决方案，它使用递归cte来生成“table of numbers”（礼貌Itzik Ben-Gan），它是useful，适用于所有问题，包括字符串拆分和PIVOT。 SQL Server 2005起。包括全表创建，插入和选择脚本。

CREATE TABLE dbo.Table1 
(
    Name  VARCHAR(30), 
    [Values] VARCHAR(128) 
) 
GO 

INSERT INTO dbo.Table1 VALUES ('John', 'val,val2,val3') 
INSERT INTO dbo.Table1 VALUES ('Peter', 'val5,val7,val9,val14') 
INSERT INTO dbo.Table1 VALUES ('Lesli', 'val8,val34,val36,val65,val71,val') 
INSERT INTO dbo.Table1 VALUES ('Amy', 'val3,val5,val99') 
GO 

SELECT * FROM dbo.Table1; 
GO 

WITH 
L0 AS(SELECT 1 AS c UNION ALL SELECT 1), 
L1 AS(SELECT 1 AS c FROM L0 AS A, L0 AS B), 
L2 AS(SELECT 1 AS c FROM L1 AS A, L1 AS B), 
L3 AS(SELECT 1 AS c FROM L2 AS A, L2 AS B), 
Numbers AS(SELECT ROW_NUMBER() OVER(ORDER BY c) AS n FROM L3) 
SELECT Name, [1] AS Column1, [2] AS Column2, [3] AS Column3, [4] AS Column4, [5] AS Column5, [6] AS Column6, [7] AS Column7 
FROM 
(SELECT Name, 
     ROW_NUMBER() OVER (PARTITION BY Name ORDER BY nums.n) AS PositionInList, 
     LTRIM(RTRIM(SUBSTRING(valueTable.[Values], nums.n, charindex(N',', valueTable.[Values] + N',', nums.n) - nums.n))) AS [Value] 
FROM Numbers AS nums INNER JOIN dbo.Table1 AS valueTable ON nums.n <= CONVERT(int, LEN(valueTable.[Values])) AND SUBSTRING(N',' + valueTable.[Values], n, 1) = N',') AS SourceTable 
PIVOT 
(
MAX([VALUE]) FOR PositionInList IN ([1], [2], [3], [4], [5], [6], [7]) 
) AS Table2 
GO 

--DROP TABLE dbo.Table1 

此输出

Name Values 
John val,val2,val3 
Peter val5,val7,val9,val14 
Lesli val8,val34,val36,val65,val71,val 
Amy val3,val5,val99 

到

Name Column1 Column2 Column3 Column4 Column5 Column6 Column7 
Amy val3 val5 val99 NULL NULL NULL NULL 
John val  val2 val3 NULL NULL NULL NULL 
Lesli val8 val34 val36 val65 val71 val  NULL 
Peter val5 val7 val9 val14 NULL NULL NULL