Need a function to get a list of values in a table

Instead of writing a function to return this data, why not simply add a new table to your database where you add these values and then use that table in your application.

In my opinion hardcoded list of values are something you want to avoid.

DECLARE @S varchar(max),
  @Split char(1),
  @X xml

SELECT @S = '1,2,3,4,5',
  @Split = ','

SELECT @X = CONVERT(xml,'<root><s>' + REPLACE(@S,@Split,'</s><s>') + '</s></root>')

SELECT [Value] = T.c.value('.','varchar(20)')
FROM @X.nodes('/root/s') T(c)

This logic will give you comma seperated value just @S input to function which is hardcoded here.

Check this.

am inserting into temptable. If you want to directly update it to your physical table , have the number column as identity column

My stored proc:

Create PROCEDURE asp_splitstrings
(@string varchar(50))
 AS 
 DECLARE @id integer = 1,
  @previous_id integer = 0,
   @value varchar(50)

create table #temp
(Number int Identity(1,1),
IntegerFromList varchar(50))
     WHILE @id > 0 
     BEGIN
      SET @id = CHARINDEX(',',@string,@previous_id+1) 
      IF @id > 0 
      BEGIN 
      SET @value = SUBSTRING(@string,@previous_id+1,@id-@previous_id-1) 
    
      INSERT INTO #temp VALUES (@value) 
      SET @previous_id = @id 
      END 
      END 
      IF @previous_id < LEN(@string) 
      BEGIN 
      SET @value = SUBSTRING(@string,@previous_id+1,LEN(@string))
       INSERT INTO #temp VALUES (@value) 
       END
select * from #temp

Execute sp now

exec asp_splitstrings 'CHOPL,NAKRL,NLGD2,DEVKD,HALYA'