T-SQL -- convert comma-delimited column into multiple columns - tsql

Question

From the table below, how can I convert the Values column into multiple columns, populated with individual values that are currently separated by commas? Before the conversion:
Name Values
---- ------
John val,val2,val3
Peter val5,val7,val9,val14
Lesli val8,val34,val36,val65,val71,val
Amy val3,val5,val99
The result of the conversion should look like:
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

First, what database product and version are you using? If you are using SQL Server 2005 and later, you can write a Split user-defined function like so:
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
)
You can then split out the values in you want using something akin to:
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

Here is a solution that uses a recursive cte to generate a "table of numbers" (courtesy of Itzik Ben-Gan), which is useful for all manner of problems including string splitting, and PIVOT. SQL Server 2005 onwards. Full table create, insert and select script included.
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
Which converts this output
Name Values
John val,val2,val3
Peter val5,val7,val9,val14
Lesli val8,val34,val36,val65,val71,val
Amy val3,val5,val99
to
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