怎么样使用SQL Server 2012开窗函数？

-- 开窗函数：在结果集的基础上进一步处理(聚合操作)
-- Over函数,添加一个字段显示最大年龄
SELECT * ,
  MAX(StuAge) OVER ( ) MaxStuAge
FROM dbo.Student;
-- Over函数,添加一个字段显示总人数
SELECT * ,
  COUNT(StuID) OVER ( ) StuCount
FROM dbo.Student;
-- Partition By 分组统计数量
-- 根据性别分组后，统计
SELECT COUNT(*) OVER ( PARTITION BY StuSex ) ,
  *
FROM dbo.Student;
-- 根据班级分组后，统计、排序
SELECT COUNT(*) OVER ( PARTITION BY Class ORDER BY Height) ,
  *
FROM dbo.Student;
-- Over函数,添加一个字段显示平均身高
SELECT * ,
  AVG(Height) OVER ( ) AgeHeight
FROM dbo.Student;
--Row_Rumber()
SELECT ROW_NUMBER() OVER ( ORDER BY StuID DESC ) RowNumber ,
  *
FROM dbo.Student
--Row_Rumber() 实现分页效果
;
WITH T AS ( SELECT ROW_NUMBER() OVER ( ORDER BY StuID DESC ) RowNumber ,
      *
    FROM  dbo.Student
    )
 SELECT *
 FROM T
 WHERE T.RowNumber BETWEEN 1 AND 3;
--Rank() 排名函数,名次相同，跳过
SELECT RANK() OVER ( ORDER BY Height ) ,
  *
FROM dbo.Student;
--DENSE_Rank() 排名函数，名次相同不跳过
SELECT DENSE_RANK() OVER ( ORDER BY Height ) ,
  *
FROM dbo.Student;
-- NTILE()函数，参数：记录总数/划分区域 = 每个区域数组，把记录序号放进数组 (平均分组)
SELECT NTILE(3) OVER ( ORDER BY StuSex ) ,
  *
FROM dbo.Student;