如何判断字段为datetime型的值为空？

      记录:
        SELECT   *   from  OA_Attendance  WHERE   UserID  = 5
        and  DATEDIFF(day,[Date],getdate()) =0  and DATEDIFF(year,[Date],getdate()) =0
        and DATEDIFF(month,[Date],getdate()) =0 and EndTime is not null