PL/SQL语法之OVER(PARTITION BY)及开窗函数

oracle的分析函数over及开窗函数
一:分析函数over
Oracle从8.1.6开始提供分析函数,分析函数用于计算基于组的某种聚合值,它和聚合函数的不同之处是
对于每个组返回多行,而聚合函数对于每个组只返回一行。
下面通过几个例子来说明其应用。
1:统计某商店的营业额。
date?????? sale
1?????????? 20
2?????????? 15
3?????????? 14
4?????????? 18
5?????????? 30
规则:按天统计:每天都统计前面几天的总额
select t.* ,sum(sale) over(order by date) sum from example t
得到的结果:
DATE?? SALE?????? SUM
—– ——– ——
1????? 20??????? 20?????????? –1天
2????? 15??????? 35?????????? –1天+2天
3????? 14??????? 49?????????? –1天+2天+3天
4????? 18??????? 67??????????? .
5????? 30??????? 97??????????? .
2:统计各班成绩第一名的同学信息
NAME?? CLASS S
—– —– ————-
fda??? 1????? 80
ffd??? 1????? 78
dss??? 1????? 95
cfe??? 2????? 74
gds??? 2????? 92
gf???? 3????? 99
ddd??? 3????? 99
3dd??? 3????? 78
查询语句:
select * from
(
select name,class,s,rank()over(partition by class order by s desc) mm from t2
)
where mm=1
得到结果:
NAME?? CLASS S????????? MM
—– —– ——?? ——-
dss??? 1????? 95??????? 1
gds??? 2????? 92??????? 1
gf???? 3????? 99??????? 1
ddd??? 3????? 99??????? 1
注意:
1.在求第一名成绩的时候,不能用row_number(),因为如果同班有两个并列第一,row_number()只返回一个结果
2.rank()和dense_rank()的区别是:
–rank()是跳跃排序,有两个第二名时接下来就是第四名
–dense_rank()l是连续排序,有两个第二名时仍然跟着第三名
3.分类统计 (并显示信息)
A?? B?? C
— — ——
m?? a?? 2
n?? a?? 3
m?? a?? 2
n?? b?? 2
n?? b?? 1
x?? b?? 3
x?? b?? 2
x?? b?? 4
h?? b?? 3
select a,c,sum(c)over(partition by a) from t2
得到结果:
A?? B?? C??????? SUM(C)OVER(PARTITIONBYA)
— — ——- ————————
h?? b?? 3??????? 3
m?? a?? 2??????? 4
m?? a?? 2??????? 4
n?? a?? 3??????? 6
n?? b?? 2??????? 6
n?? b?? 1??????? 6
x?? b?? 3??????? 9
x?? b?? 2??????? 9
x?? b?? 4??????? 9
如果用sum,group by 则只能得到
A?? SUM(C)
— ———————-
h?? 3
m?? 4
n?? 6
x?? 9
无法得到B列值
—将B栏位值相同的对应的C 栏位值加总,数据:
A B C
1 1 1
1 2 2
1 3 3
2 2 5
3 4 6
select a,b,c, SUM(C) OVER (PARTITION BY B) C_Sum
from test
查询结果:
A B C C_SUM
1 1 1 1
1 2 2 7
2 2 5 7
1 3 3 3
3 4 6 6
—如果不需要以某个栏位的值分割,那就要用null,这样就会将C的栏位值sum放在每行后面,也可以直接空着,不需要填写,如over()
select a,b,c, SUM(C) OVER (PARTITION BY null) C_Sum
from test
A B C C_SUM
1 1 1 17
1 2 2 17
1 3 3 17
2 2 5 17
3 4 6 17
求个人工资占部门工资的百分比
NAME DEPT SAL
———- —- —–
a??? 10?? 2000
b??? 10?? 3000
c??? 10?? 5000
d??? 20?? 4000
SQL> select name,dept,sal,sal*100/sum(sal) over(partition by dept) percent from salary;
NAME DEPT SAL PERCENT
———- —- —– ———-
a??? 10?? 2000 20
b??? 10?? 3000 30
c??? 10?? 5000 50
d??? 20?? 4000 100
二:开窗函数
开窗函数指定了分析函数工作的数据窗口大小,这个数据窗口大小可能会随着行的变化而变化,举例如下:
over(order by salary) 按照salary排序进行累计,order by是个默认的开窗函数
over(partition by deptno)按照部门分区
over(order by salary range between 5 preceding and 5 following)
每行对应的数据窗口是之前行幅度值不超过5,之后行幅度值不超过5
例如:对于以下列
aa
1
2
2
2
3
4
5
6
7
9
sum(aa)over(order by aa range between 2 preceding and 2 following)
得出的结果是
AA?????????????????????? SUM
———————- ———————–
1?????????????????????? 10
2?????????????????????? 14
2?????????????????????? 14
2?????????????????????? 14
3?????????????????????? 18
4?????????????????????? 18
5?????????????????????? 22
6?????????????????????? 18
7?????????????????????? 22
9?????????????????????? 9
就是说,对于aa=5的一行 ,sum为?? 5-1<=aa<=5+2 的和
对于aa=2来说 ,sum=1+2+2+2+3+4=14???? ;
又如 对于aa=9 ,9-1<=aa<=9+2 只有9一个数,所以sum=9??? ;
over(order by salary rows between 2 preceding and 4 following)
每行对应的数据窗口是之前2行,之后4行
下面三条语句等效:
over(order by salary rows between unbounded preceding and unbounded following)
每行对应的数据窗口是从第一行到最后一行,等效:
over(order by salary range between unbounded preceding and unbounded following)
等效over(partition by null)
语法:ROW_NUMBER() OVER(PARTITION BY COLUMN ORDER BY COLUMN)
简单的说row_number()从1开始,为每一条分组记录返回一个数字,这里的ROW_NUMBER() OVER (ORDER BY xlh DESC) 是先把xlh列降序,再为降序以后的没条xlh记录返回一个序号。
示例:
xlh?????????? row_num
1700????????????? 1
1500????????????? 2
1085????????????? 3
710?????????????? 4
row_number() OVER (PARTITION BY COL1 ORDER BY COL2) 表示根据COL1分组,在分组内部根据 COL2排序,而此函数计算的值就表示每组内部排序后的顺序编号(组内连续的唯一的)
实例:
create table employee (empid int ,deptid int ,salary decimal(10,2))
insert into employee values(1,10,5500.00)
insert into employee values(2,10,4500.00)
insert into employee values(3,20,1900.00)
insert into employee values(4,20,4800.00)
insert into employee values(5,40,6500.00)
insert into employee values(6,40,14500.00)
insert into employee values(7,40,44500.00)
insert into employee values(8,50,6500.00)
insert into employee values(9,50,7500.00)
数据显示为
empid?????? deptid????? salary
———– ———– ——————-
1?????????? 10????????? 5500.00
2?????????? 10????????? 4500.00
3?????????? 20????????? 1900.00
4?????????? 20????????? 4800.00
5?????????? 40????????? 6500.00
6?????????? 40????????? 14500.00
7?????????? 40????????? 44500.00
8?????????? 50????????? 6500.00
9?????????? 50????????? 7500.00
需求:根据部门分组,显示每个部门的工资等级
预期结果:
empid?????? deptid????? salary???????????? rank
———– ———– ————— ———-
1?????????? 10????????? 5500.00??????????? 1
2?????????? 10????????? 4500.00??????????? 2
4?????????? 20????????? 4800.00??????????? 1
3?????????? 20????????? 1900.00??????????? 2
7?????????? 40????????? 44500.00?????????? 1
6?????????? 40????????? 14500.00?????????? 2
5?????????? 40????????? 6500.00??????????? 3
9?????????? 50????????? 7500.00??????????? 1
8?????????? 50????????? 6500.00??????????? 2

SQL脚本:
SELECT *, Row_Number() OVER (partition by deptid ORDER BY salary desc) rank FROM employee



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“PL/SQL语法之OVER(PARTITION BY)及开窗函数”有1条评论

Bethany Rice | 2012-01-20 18:24 |

学习了,谢谢分享!