Create Shortcut Function in T-SQL - sql

Question

Using the code below I can create a comma separated list of results from the results of a select statement:
DECLARE #lst NVARCHAR(MAX) = ''
SELECT #lst = COALESCE(NULLIF(#lst,'')+N',',N'') + [colName]
FROM [tableName]
I would like to transform this into a sort of shortcut function, for example:
SELECT dbo.fnColAsList([colName])
FROM [tableName]
Is this at all possible?
Edit:
To give an example, if the select statement returned the following 3 columns:
SELECT [colName] FROM [tableName]
>>> colName
-----------
[1] foo1
[2] foo2
[3] foo3
Then the code would produce a single varchar field:
SELECT #lst = COALESCE(NULLIF(#lst,'')+N',',N'') + [colName]
FROM [tableName];
SELECT #lst
>>> lst
---------
[1] foo1,foo2,foo3
I wish to produce a shortcut so that I can call the code around any column so for example I could do this:
SELECT fnColAsList(colName) AS 'x' FROM [tab1];
>>> x
-----------------
[1] tab1Col1,tab1Col2,tab1Coln
SELECT fnColAsList(colName) AS 'y' FROM [tab2];
>>> y
-----------------
[1] tab2Col1,tab2Col2,tab2Coln
Answered:
CREATE FUNCTION dbo.fnColAsList(#rawxml XML)
RETURNS NVARCHAR(MAX)
AS
BEGIN
RETURN STUFF(((SELECT ',' + AllAttribs.value(N'.','nvarchar(max)')
FROM #rawxml.nodes('/row/#*') x (AllAttribs)
FOR XML PATH(''),ROOT('x'),TYPE).value('/x[1]','VARCHAR(MAX)')
),1,1,'');
END
GO
SELECT dbo.fnColAsList((SELECT [colName] FROM tabName FOR XML RAW))

Answer 1

You can try a trick: Pass in the SELECT as XML by wrapping it in paranthesis. XML is - other than pure SQL - much mightier in dealing with generic names:
CREATE FUNCTION dbo.TestCSV(#SelectForXMLRaw XML)
RETURNS NVARCHAR(MAX)
AS
BEGIN
RETURN STUFF(
(
SELECT ',' + AllAttribs.value(N'.','nvarchar(max)')
FROM #SelectForXMLRaw.nodes('/row/#*') x(AllAttribs)
FOR XML PATH(''),TYPE
).value(N'.','nvarchar(max)'),1,1,''
);
END
GO
DECLARE #tbl TABLE(ID INT IDENTITY,col1 VARCHAR(100),col2 VARCHAR(100),col3 VARCHAR(100));
INSERT INTO #tbl VALUES ('1a','2a','3a'),('1b','2b','3b');
SELECT ID
,dbo.TestCSV((SELECT * FROM #tbl AS t2 WHERE t2.ID=t.ID FOR XML RAW)) AS Concatenated
FROM #tbl AS t
GO
DROP FUNCTION dbo.TestCSV;
The result
ID Concatenated
1 1,1a,2a,3a
2 2,1b,2b,3b
UPDATE According to your edits
From you edits I take, that you need this for row-wise data. You can achieve this with the same function actually. Just try this
DECLARE #tbl2 TABLE(SomeUnknownColumn VARCHAR(100));
INSERT INTO #tbl2 VALUES ('Val 1'),('Val 2'),('Val 3');
SELECT dbo.TestCSV((SELECT * FROM #tbl2 FOR XML RAW)) AS Concatenated
Thne result:
Val 1,Val 2,Val 3