Function takes a string and section number of string which is required and separator, which separates different sections of given string

usp_stringpart.sql

--| Create By: Aasim Abdullah
--| Description: Function takes a string and section number of string which
--|              is required and separator, which separates different
--|              sections of given string
--| How To Use: SELECT dbo.usp_stringpart('First,Second,Third,Forth,Fifth',3,',')

CREATE FUNCTION dbo.usp_stringpart
    (
      @InputString NVARCHAR(1000),
      @Section SMALLINT,
      @Separator NCHAR(1)
    )
RETURNS NVARCHAR(1000)
BEGIN
    DECLARE @StartPosition INT,
        @EndPosition INT,
        @Cycle INT,
        @ResultString NVARCHAR(1000)

    SELECT  @Cycle = 0,
            @StartPosition = 0

    WHILE @Cycle < @Section - 1
        BEGIN
            SELECT  @StartPosition = CHARINDEX(@Separator, @InputString,
                                               @StartPosition) + 1
            IF @StartPosition = 1 
                SELECT  @Cycle = @Section
            ELSE 
                SELECT  @Cycle = @Cycle + 1
                                         
                 
        END

    SELECT  @EndPosition = CHARINDEX(@Separator, @InputString, @StartPosition)
    SELECT  @ResultString = LTRIM(RTRIM(SUBSTRING(@InputString, @StartPosition,
                                                  CASE @EndPosition
                                                    WHEN 0
                                                    THEN ( LEN(@InputString)
                                                           + 1 )
                                                         - @StartPosition
                                                    ELSE ( @EndPosition
                                                           - @StartPosition )
                                                  END)))
     
    RETURN @ResultString

END