CREATE PROCEDURE [dbo].[CreateCalendar] 
/************************************************************************************************************
 Purpose: 
 Given a start date and an end date, create a calendar of dates that easily traverses months and years.  Is
 capable of generating up to 179 years worth of calendar by month in any given run. 
 Usage Notes: 
 1.  End date parameter is optional... if not provided, the start date will be used to return that one month.
 2.  Of the two input paramters, the lowest (earliest) date will be used as the start date regardless of the
     order provided. 
 3.  Returns a single result set containing all dates. 
 4.  Does NOT use a Cursor, While Loop, Temp Table, or Table variable so that even really picky DBA's won't
     reject the code. 
 5.  Because only set-based code was used, returns 10 years worth of calendar in about 230 milliseconds. 
     A full year takes a scant 76 milliseconds and a single month takes 63 milliseconds. A hundred-year 
     calendar takes only 6.3 seconds. 
 6.  The start date does NOT need to be the first of the month and the end date does NOT need to be the last
     day of the month.  The internal calculations will "auto-magically" include the whole month for both the 
     start and end dates as well as all months in between. 
 Revision History: 
 Rev 00 - 08/13/2007 - Jeff Moden - Initial creation and unit test. 
************************************************************************************************************/
--===== Declare the input parameters 
        @pStartDate DATETIME,              --Any date (can include time) in the desired start month 
        @pEndDate   DATETIME = @pStartDate --Any date (can include time) in the desired end month 
     AS 
--===== Create the correct environment 
    SET NOCOUNT ON --Suppress the auto-display of rowcounts to prevent false echos on GUI's 
    SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED --Same as putting WITH (NOLOCK) on tables in query 
--===== Create the base date that all the calculations rely on (is a Monday) 
DECLARE @BaseDate DATETIME 
    SET @BaseDate = '1753-01-01' 
--===== Make sure the inputs are in the correct order (start date must always be the earliest date)
     IF @pEndDate < @pStartDate 
  BEGIN 
        DECLARE @Swap DATETIME 
         SELECT @Swap       = @pStartDate, 
                @pStartDate = @pEndDate, 
                @pEndDate   = @Swap 
    END     
--===== Modify the start to start on the first of the same month and the end date to end on the last day 
     -- of the same month. 
    SET @pStartDate = DATEADD(mm,DATEDIFF(mm,@BaseDate,@pStartDate),@BaseDate) 
    SET @pEndDate   = DATEADD(mm,DATEDIFF(mm,@BaseDate,@pEndDate)+1,@BaseDate)-1 

--===== Create the calendar without loops, cursors, or temp tables 
 SELECT MAX(DATENAME(yy,d.TheDate)) AS [Year], 
        MAX(LEFT(DATENAME(mm,d.TheDate),3))AS [Month], 
        MAX(CASE WHEN DATENAME(dw,d.TheDate) = '월요일'    THEN DATENAME(dd,d.TheDate) ELSE '' END) AS Mon, 
        MAX(CASE WHEN DATENAME(dw,d.TheDate) = '화요일'   THEN DATENAME(dd,d.TheDate) ELSE '' END) AS Tue, 
        MAX(CASE WHEN DATENAME(dw,d.TheDate) = '수요일' THEN DATENAME(dd,d.TheDate) ELSE '' END) AS Wed, 
        MAX(CASE WHEN DATENAME(dw,d.TheDate) = '목요일'  THEN DATENAME(dd,d.TheDate) ELSE '' END) AS Thu, 
        MAX(CASE WHEN DATENAME(dw,d.TheDate) = '금요일'    THEN DATENAME(dd,d.TheDate) ELSE '' END) AS Fri, 
        MAX(CASE WHEN DATENAME(dw,d.TheDate) = '토요일'  THEN DATENAME(dd,d.TheDate) ELSE '' END) AS Sat, 
        MAX(CASE WHEN DATENAME(dw,d.TheDate) = '일요일'    THEN DATENAME(dd,d.TheDate) ELSE '' END) AS Sun 
   FROM (--==== Derived table "d" finds all dates for the given range of dates up to 65535 days apart 
         SELECT YEAR(@pStartDate+n.Number)                    AS TheYear, 
                MONTH(@pStartDate+n.Number)                   AS TheMonth, 
                DATEDIFF(dd,@BaseDate,@pStartDate+n.Number)/7 AS TheWeek, 
                @pStartDate+n.Number                          AS TheDate 
           FROM (--==== Derived table "n" creates numbers from 0 to 65535 (about 179 years worth of days) 
                 SELECT t1.Number*256+t2.Number AS Number 
                   FROM Master.dbo.spt_Values t1, 
                        Master.dbo.spt_Values t2 
                  WHERE t1.Type = 'P' 
                    AND t2.Type = 'P' 
                )n 
          WHERE @pStartDate+n.Number <= @pEndDate 
        )d 
  GROUP BY d.TheYear,d.TheMonth,d.TheWeek 
  ORDER BY d.TheYear,d.TheMonth,d.TheWeek