drop and create SQL Server procedure simple way

 IF EXISTS (SELECT * FROM sys.objects WHERE type = 'P' AND name = 'USP_BookTypes')

DROP PROCEDURE USP_BookTypes

GO

CREATE  PROC USP_BookTypes

(

   @action varchar(20)

  ,@BookTypeId int=null

  ,@BookType varchar(100)=null

)

AS BEGIN

  IF(@action='SELECTALL')

   BEGIN

    SELECT B.BookTypeId,B.BookType FROM BookTypes B WITH(NOLOCK)  

WHERE B.IsActive='Y'  order by B.BookTypeId; 

   END

   ELSE IF(@action='SELECTBYID')

   BEGIN

    SELECT B.BookTypeId,B.BookType FROM BookTypes B WITH(NOLOCK)  

WHERE B.BookTypeId=@BookTypeId and B.IsActive='Y' order by B.BookTypeId; 

   END

 END