user-defined functions in SQL

CREATE FUNCTION [dbo].[fnNthIndex](@Input VARCHAR(8000), @Delimiter CHAR(1), @Ordinal INT)
/**************************************************************************
CREATED BY	: Prabu
CREATED DATE   : 21-Feb-2013
PURPOSE		: To Find the Nth occurrence of a substring

USAGE		:
			

		SELECT dbo.fnNthIndex('ü123ü124ü27339ü', 'ü', 2)
		

***************************************************************************/
RETURNS INT
AS
BEGIN
    DECLARE  @Pointer INT=1,@Last INT=0, @Count INT=1
    WHILE (2 > 1)
    BEGIN
        SET @Pointer = CHARINDEX(@Delimiter,@Input,@Pointer)
        IF @Pointer = 0
            BREAK
        IF @Count = @Ordinal
	   BEGIN
            SET @Last = @Pointer
            BREAK
        END
        SELECT @Count = @Count + 1, @Pointer = @Pointer + 1
      END
    RETURN @Last
END

USE AdventureWorks2012;
GO
IF OBJECT_ID (N'dbo.ISOweek', N'FN') IS NOT NULL
    DROP FUNCTION dbo.ISOweek;
GO
CREATE FUNCTION dbo.ISOweek (@DATE datetime)
RETURNS int
WITH EXECUTE AS CALLER
AS
BEGIN
     DECLARE @ISOweek int;
     SET @ISOweek= DATEPART(wk,@DATE)+1
          -DATEPART(wk,CAST(DATEPART(yy,@DATE) as CHAR(4))+'0104');
--Special cases: Jan 1-3 may belong to the previous year
     IF (@ISOweek=0) 
          SET @ISOweek=dbo.ISOweek(CAST(DATEPART(yy,@DATE)-1 
               AS CHAR(4))+'12'+ CAST(24+DATEPART(DAY,@DATE) AS CHAR(2)))+1;
--Special case: Dec 29-31 may belong to the next year
     IF ((DATEPART(mm,@DATE)=12) AND 
          ((DATEPART(dd,@DATE)-DATEPART(dw,@DATE))>= 28))
          SET @ISOweek=1;
     RETURN(@ISOweek);
END;
GO
SET DATEFIRST 1;
SELECT dbo.ISOweek(CONVERT(DATETIME,'12/26/2004',101)) AS 'ISO Week';

CREATE FUNCTION Example( @TableName TableType READONLY)
RETURNS VARCHAR(50)
AS
BEGIN
    DECLARE @name VARCHAR(50)

    SELECT TOP 1 @name = LocationName FROM @TableName
    RETURN @name
END