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;