SET ANSI_NULLS ON

GO



SET QUOTED_IDENTIFIER ON

GO



CREATE FUNCTION [dbo].[udf_getNthOccuranceOfWeekDay]

    (

      @year INT ,

      @month TINYINT ,

      @weekday TINYINT ,

      @iOccAt TINYINT

    )

RETURNS DATETIME

AS 

    BEGIN

        DECLARE @dt DATETIME ,

            @retDate DATETIME

   

        SET @dt = CAST(@year AS CHAR(4)) + '-' + CAST(@month AS CHAR(2)) + '-01'



        IF ( MONTH(DATEADD(DAY, @weekday - DATEPART(DW, @dt), @dt)) = @month ) 

            BEGIN 

                IF ( MONTH(DATEADD(WEEK, @iOccAt - 1, DATEADD(DAY, @weekday - DATEPART(DW, @dt), @dt))) = @month ) 

                    SET @retDate = DATEADD(WEEK, @iOccAt - 1, DATEADD(DAY, @weekday - DATEPART(DW, @dt), @dt))

                ELSE 

                    SET @retDate = DATEADD(WEEK, @iOccAt - 2, DATEADD(DAY, @weekday - DATEPART(DW, @dt), @dt))

            END

        ELSE 

            BEGIN   

                IF ( MONTH(DATEADD(WEEK, @iOccAt, DATEADD(DAY, @weekday - DATEPART(DW, @dt), @dt))) = @month ) 

                    SET @retDate = DATEADD(WEEK, @iOccAt, DATEADD(DAY, @weekday - DATEPART(DW, @dt), @dt))

                ELSE 

                    SET @retDate = DATEADD(WEEK, @iOccAt - 1, DATEADD(DAY, @weekday - DATEPART(DW, @dt), @dt))

            END   

        RETURN @retDate 

    END



GO