http://zonghl8006.blog.163.com/blog/static/4528311520083995931317/

? over(Partition by...) 一個超級牛皮的ORACLE特有函數。

天天都用ORACLE，用了快2年了。最近才接觸到這個功能強大而靈活的函數。真實慚愧啊！

oracle的分析函數over 及開窗函數
一：分析函數over
Oracle從8.1.6開始提供分析函數，分析函數用于計算基于組的某種聚合值，它和聚合函數的不同之處是
對于每個組返回多行，而聚合函數對于每個組只返回一行。?
下面通過幾個例子來說明其應用。???????????????????????????????????????
1：統計某商店的營業額。????????
???? date?????? sale
???? 1?????????? 20
???? 2?????????? 15
???? 3?????????? 14
???? 4?????????? 18
???? 5?????????? 30
??? 規則：按天統計：每天都統計前面幾天的總額
??? 得到的結果：
??? 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:統計各班成績第一名的同學信息
??? NAME?? CLASS S?????????????????????????
??? ----- ----- ----------------------?
??? fda??? 1????? 80?????????????????????
??? ffd??? 1????? 78?????????????????????
??? dss??? 1????? 95?????????????????????
??? cfe??? 2????? 74?????????????????????
??? gds??? 2????? 92?????????????????????
??? gf???? 3????? 99?????????????????????
??? ddd??? 3????? 99?????????????????????
??? adf??? 3????? 45?????????????????????
??? asdf?? 3????? 55?????????????????????
??? 3dd??? 3????? 78??????????????
???
??? 通過：???
??? --
??? select * from???????????????????????????????????????????????????????????????????????
??? (????????????????????????????????????????????????????????????????????????????
??? select name,class,s,rank()over(partition by class order by s desc) mm from t2
??? )????????????????????????????????????????????????????????????????????????????
??? where mm=1?
??? --
??? 得到結果：
??? NAME?? CLASS S?????????????????????? MM????????????????????????????????????????????????????????????????????????????????????????
??? ----- ----- ---------------------- ----------------------?
??? dss??? 1????? 95????????????????????? 1??????????????????????
??? gds??? 2????? 92????????????????????? 1??????????????????????
??? gf???? 3????? 99????????????????????? 1??????????????????????
??? ddd??? 3????? 99????????????????????? 1??????????
???
??? 注意：
??? 1.在求第一名成績的時候，不能用row_number()，因為如果同班有兩個并列第一，row_number()只返回一個結果?????????
??? 2.rank()和dense_rank()的區別是：
????? --rank()是跳躍排序，有兩個第二名時接下來就是第四名
????? --dense_rank()l是連續排序，有兩個第二名時仍然跟著第三名
?????
?????
3.分類統計 (并顯示信息)
??? 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????????????????
?? 得到結果：
?? 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 則只能得到
?? A?? SUM(C)????????????????????????????
?? -- ----------------------?
?? h?? 3??????????????????????
?? m?? 4??????????????????????
?? n?? 6??????????????????????
?? x?? 9??????????????????????
?? 無法得到B列值???????
??
＝＝＝＝＝
select * from test

數據:
A B C?
1 1 1?
1 2 2?
1 3 3?
2 2 5?
3 4 6

---將B欄位值相同的對應的C 欄位值加總
select a,b,c, SUM(C) OVER (PARTITION BY B) C_Sum
from test

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

?

---如果不需要已某個欄位的值分割,那就要用 null

eg: 就是將C的欄位值summary 放在每行后面

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

?

求個人工資占部門工資的百分比

SQL> select * from salary;

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：開窗函數???????????
????? 開窗函數指定了分析函數工作的數據窗口大小，這個數據窗口大小可能會隨著行的變化而變化，舉例如下：?
1：?????
?? over（order by salary） 按照salary排序進行累計，order by是個默認的開窗函數
?? over（partition by deptno）按照部門分區
2：
? over（order by salary range between 5 preceding and 5 following）
?? 每行對應的數據窗口是之前行幅度值不超過5，之后行幅度值不超過5
?? 例如:對于以下列
???? aa
???? 1
???? 2
???? 2
???? 2
???? 3
???? 4
???? 5
???? 6
???? 7
???? 9
???
?? sum(aa)over（order by aa range between 2 preceding and 2 following）
?? 得出的結果是
??????????? AA?????????????????????? SUM
??????????? ---------------------- -------------------------------------------------------?
??????????? 1?????????????????????? 10??????????????????????????????????????????????????????
??????????? 2?????????????????????? 14??????????????????????????????????????????????????????
??????????? 2?????????????????????? 14??????????????????????????????????????????????????????
??????????? 2?????????????????????? 14??????????????????????????????????????????????????????
??????????? 3?????????????????????? 18??????????????????????????????????????????????????????
??????????? 4?????????????????????? 18??????????????????????????????????????????????????????
??????????? 5?????????????????????? 22??????????????????????????????????????????????????????
??????????? 6?????????????????????? 18????????????????????????????????????????????????????????????????
??????????? 7?????????????????????? 22????????????????????????????????????????????????????????????????
??????????? 9?????????????????????? 9?????????????????????????????????????????????????????????????????
?????????????
?? 就是說，對于aa=5的一行 ，sum為?? 5-1<=aa<=5+2 的和
?? 對于aa=2來說 ，sum=1+2+2+2+3+4=14???? ；
?? 又如 對于aa=9 ，9-1<=aa<=9+2 只有9一個數，所以sum=9??? ；
??????????????
3：其它：
???? over（order by salary rows between 2 preceding and 4 following）
????????? 每行對應的數據窗口是之前2行，之后4行?
4：下面三條語句等效：???????????
???? over（order by salary rows between unbounded preceding and unbounded following）
????????? 每行對應的數據窗口是從第一行到最后一行，等效：
???? over（order by salary range between unbounded preceding and unbounded following）
?????????? 等效
???? over(partition by null)

?

常用的分析函數如下所列:

row_number() over(partition by ... order by ...)
rank() over(partition by ... order by ...)
dense_rank() over(partition by ... order by ...)
count() over(partition by ... order by ...)
max() over(partition by ... order by ...)
min() over(partition by ... order by ...)
sum() over(partition by ... order by ...)
avg() over(partition by ... order by ...)
first_value() over(partition by ... order by ...)
last_value() over(partition by ... order by ...)
lag() over(partition by ... order by ...)
lead() over(partition by ... order by ...)

示例
SQL> select type,qty from test;

TYPE QTY
---------- ----------
1 6
2 9

?SQL> select type,qty,to_char(row_number() over(partition by type order by qty))||'/'||to_char(count(*) over(partition by type)) as cnt2 from test;

TYPE QTY CNT2?
---------- ---------- ------------
3 1/2
1 6 2/2
2 5 1/3
7 2/3?
2 9 3/3

?SQL> select * from test;
---------- -------------------------------------------------
1 11111
2 22222
3 33333
4 44444

SQL> select t.id,mc,to_char(b.rn)||'/'||t.id)e
2 from test t,
?(select rownum rn from (select max(to_number(id)) mid from test) connect by rownum <=mid ))L
4 where b.rn<=to_number(t.id)
order by id

ID MC TO_CHAR(B.RN)||'/'||T.ID
--------- -------------------------------------------------- ---------------------------------------------------
1 11111 1/1
2 22222 1/2
2 22222 2/2
3 33333 1/3
3 33333 2/3
3 33333 3/3
?44444 1/4 44444 2/4
4 44444 3/4CNOUG4 44444 4/4

10 rows selected

*******************************************************************

關于partition by

這些都是分析函數，好像是8.0以后才有的 row_number()和rownum差不多，功能更強一點（可以在各個分組內從1開時排序） rank()是跳躍排序，有兩個第二名時接下來就是第四名（同樣是在各個分組內） dense_rank()l是連續排序，有兩個第二名時仍然跟著第三名。相比之下row_number是沒有重復值的 lag（arg1,arg2,arg3): arg1是從其他行返回的表達式 arg2是希望檢索的當前行分區的偏移量。是一個正的偏移量，時一個往回檢索以前的行的數目。 arg3是在arg2表示的數目超出了分組的范圍時返回的值。

1.
select deptno,row_number() over(partition by deptno order by sal) from emp order by deptno;
2.
select deptno,rank() over (partition by deptno order by sal) from emp order by deptno;
3.
select deptno,dense_rank() over(partition by deptno order by sal) from emp order by deptno;
4.
select deptno,ename,sal,lag(ename,1,null) over(partition by deptno order by ename) from emp ord er by deptno;
5.
select deptno,ename,sal,lag(ename,2,'example') over(partition by deptno order by ename) from em p
order by deptno;
6.
select deptno, sal,sum(sal) over(partition by deptno) from emp;--每行記錄后都有總計值? select deptno, sum(sal) from emp group by deptno;
7. 求每個部門的平均工資以及每個人與所在部門的工資差額

select deptno,ename,sal ,
???? round(avg(sal) over(partition by deptno)) as dept_avg_sal,?
???? round(sal-avg(sal) over(partition by deptno)) as dept_sal_diff
from emp;

轉載于:https://www.cnblogs.com/hailei/p/4494066.html

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