CREATE FUNCTION usf_SplitString (@delimitedString nvarchar(max), @mDelimiter char(1) = 'y')
Returns @tblStringToTable Table (Colvalue nvarchar(50))
AS
BEGIN
Declare @colvalue nvarchar(50)
Declare @startpos int, @length int
while LEN(@delimitedString) > 0
BEGIN
  SET @StartPos = CHARINDEX(@mDelimiter, @DelimitedString)
  IF @StartPos < 0 set @StartPos = 0
  SET @Length = LEN(@DelimitedString) - @StartPos - 1
  IF @Length < 0 SET @Length = 0
  IF @StartPos > 0
  BEGIN
    SET @colvalue = SUBSTRING(@delimitedString,1,@StartPos - 1)
    Set @delimitedString = SUBSTRING(@delimitedString. @StartPos+ 1, LEN(@delimitedString ) - @StartPos)
END

Else
BEGIN

 Set @colvalue = @delimitedString;
 Set @delimitedString = ''
END
IF @Colvalue != ''
   IF not exists(Select 1 from @delimitedString where Colvalue = @Colvalue)
     INSERT @tblStringToTable (Colvalue)  VALUES (@Colvalue)
END
   RETURN
END
GO

See Below for example usage - don't forget you must specify database owner

select * from dbo.usf_SplitString ('1,2,3,4',',')

Returns a table

 Colvalue
1
2
3
4