T-SQL - Pivot/Crosstab - variable number of values - tsql

Question

I have a simple data set that looks like this:
Name Code
A A-One
A A-Two
B B-One
C C-One
C C-Two
C C-Three
I want to output it so it looks like this:
Name Code1 Code2 Code3 Code4 Code...n ...
A A-One A-Two
B B-One
C C-One C-Two C-Three
For each of the 'Name' values, there can be an undetermined number of 'Code' values.
I have been looking at various examples of Pivot SQL [including simple Pivot sql and sql using the XML function?] but I have not been able to figure this out - or to understand if it is even possible.
I would appreciate any help or pointers.
Thanks!

Answer 1

Try it like this:
DECLARE #tbl TABLE([Name] VARCHAR(100),Code VARCHAR(100));
INSERT INTO #tbl VALUES
('A','A-One')
,('A','A-Two')
,('B','B-One')
,('C','C-One')
,('C','C-Two')
,('C','C-Three');
SELECT p.*
FROM
(
SELECT *
,CONCAT('Code',ROW_NUMBER() OVER(PARTITION BY [Name] ORDER BY Code)) AS ColumnName
FROM #tbl
)t
PIVOT
(
MAX(Code) FOR ColumnName IN (Code1,Code2,Code3,Code4,Code5 /*add as many as you need*/)
)p;
This line
,CONCAT('Code',ROW_NUMBER() OVER(PARTITION BY [Name] ORDER BY Code)) AS ColumnName
will use a partitioned ROW_NUMBER in order to create numbered column names per code. The rest is simple PIVOT...
UPDATE: A dynamic approach to reflect the max amount of codes per group
CREATE TABLE TblTest([Name] VARCHAR(100),Code VARCHAR(100));
INSERT INTO TblTest VALUES
('A','A-One')
,('A','A-Two')
,('B','B-One')
,('C','C-One')
,('C','C-Two')
,('C','C-Three');
DECLARE #cols VARCHAR(MAX);
WITH GetMaxCount(mc) AS(SELECT TOP 1 COUNT([Code]) FROM TblTest GROUP BY [Name] ORDER BY COUNT([Code]) DESC)
SELECT #cols=STUFF(
(
SELECT CONCAT(',Code',Nmbr)
FROM
(SELECT TOP((SELECT mc FROM GetMaxCount)) ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) FROM master..spt_values) t(Nmbr)
FOR XML PATH('')
),1,1,'');
DECLARE #sql VARCHAR(MAX)=
'SELECT p.*
FROM
(
SELECT *
,CONCAT(''Code'',ROW_NUMBER() OVER(PARTITION BY [Name] ORDER BY Code)) AS ColumnName
FROM TblTest
)t
PIVOT
(
MAX(Code) FOR ColumnName IN (' + #cols + ')
)p;';
EXEC(#sql);
GO
DROP TABLE TblTest;
As you can see, the only part which will change in order to reflect the actual amount of columns is the list in PIVOTs IN() clause.
You can create a string, which looks like Code1,Code2,Code3,...CodeN and build the statement dynamically. This can be triggered with EXEC().
I'd prefer the first approach. Dynamically created SQL is very mighty, but can be a pain in the neck too...