نحوه محاسبه Median در SQL Server

CREATE PROCEDURE uspCalcMedian
(
   @tablename VARCHAR(50),
   @columnname VARCHAR(50),
   @result SQL_VARIANT OUTPUT
)
AS
BEGIN
   DECLARE @sqlstmt VARCHAR(200)
   DECLARE @midCount INT
   SET NOCOUNT ON
   SET @sqlstmt = 'insert #tempmedian select ' @columnname
       ' from ' @tablename ' order by 1 asc '
   CREATE TABLE #tempmedian (col SQL_VARIANT)
   EXEC (@sqlstmt)
   DECLARE c_med CURSOR SCROLL FOR SELECT * FROM #tempmedian
   SELECT @midCount = ROUND(COUNT(*) * 0.5,0 ) FROM #tempmedian
   OPEN c_med
   FETCH ABSOLUTE @midCount FROM c_med INTo @result
   CLOSE c_med
   DEALLOCATE c_med
   DROP TABLE #tempmedian
END