how to select comma separated vaues in sql code example

Example 1: sql server: select column values as comma separated string

DECLARE @SQL AS VARCHAR(8000)
SELECT @SQL = ISNULL(@SQL+',','') + ColumnName FROM TableName
SELECT @SQL

Example 2: sqlserver: can we select from comma seperated string variable value

/****** Object:  UserDefinedFunction [dbo].[CSVToTable]    Script Date: 04/28/2013 10:45:17 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE FUNCTION [dbo].[CSVToTable] (@InStr VARCHAR(MAX))
RETURNS @TempTab TABLE
   (id int not null)
AS
BEGIN
    ;-- Ensure input ends with comma
	SET @InStr = REPLACE(@InStr + ',', ',,', ',')
	DECLARE @SP INT
DECLARE @VALUE VARCHAR(1000)
WHILE PATINDEX('%,%', @INSTR ) <> 0 
BEGIN
   SELECT  @SP = PATINDEX('%,%',@INSTR)
   SELECT  @VALUE = LEFT(@INSTR , @SP - 1)
   SELECT  @INSTR = STUFF(@INSTR, 1, @SP, '')
   INSERT INTO @TempTab(id) VALUES (@VALUE)
END
	RETURN
END
GO