-- 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;