欧美bbbwbbbw肥妇,免费乱码人妻系列日韩,一级黄片

Oracle常見分析函數(shù)實(shí)例詳解

 更新時間：2023年04月25日 09:25:26   作者：博弈星宇  
分析函數(shù)是Oracle專門用于解決復(fù)雜報表統(tǒng)計需求的功能強(qiáng)大的函數(shù),它可以在數(shù)據(jù)行分組然后計算基于組的某種統(tǒng)計值,并且每一組的每一行都可以返回一個統(tǒng)計,下面這篇文章主要給大家介紹了關(guān)于Oracle常見分析函數(shù)的相關(guān)資料,需要的朋友可以參考下

1. 認(rèn)識分析函數(shù)

1.1 什么是分析函數(shù)

       分析函數(shù)是Oracle專門用于解決復(fù)雜報表統(tǒng)計需求的功能強(qiáng)大的函數(shù)，它可以在數(shù)據(jù)中進(jìn)行分組然后計算基于組的某種統(tǒng)計值，并且每一組的每一行都可以返回一個統(tǒng)計值。

1.2 分析函數(shù)和聚合函數(shù)的不同

      普通的聚合函數(shù)用group by分組，每個分組返回一個統(tǒng)計值；而分析函數(shù)采用partition by 分組，并且每組每行都可以返回一個統(tǒng)計值。

1.3 分析函數(shù)的形式

       分析函數(shù)帶有一個開窗函數(shù)over(),包含三個分析子句：分組(partition by)，排序(order by),  窗口(rows)，他們的使用形式如下：

over(partition by xxx  order by yyy rows between zzz)
-- 例如在scott.emp表中：xxx為deptno, yyy為sal, 
-- zzz為unbounded preceding and unbounded following

分析函數(shù)的例子：

顯示各部門員工的工資，并附帶顯示該部分的最高工資。

SQL如下： 

SELECT DEPTNO, EMPNO, ENAME, SAL, LAST_VALUE(SAL) OVER (PARTITION BY DEPTNO 
ORDER BY SAL ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) MAX_SAL 
FROM EMP;

結(jié)果為：

注： current row   表示當(dāng)前行

        unbounded preceding  表示第一行

        unbounded following    表示最后一行

last_value(sal) 的結(jié)果與 order by sal 排序有關(guān)。如果排序?yàn)閛rder by sal desc, 則最終的結(jié)果為分組排序后sal的最小值(分組排序后的最后一個值), 當(dāng)deptno為10時，max_sal為1300。

2. 理解over()函數(shù)

2.1 兩個order by 的執(zhí)行機(jī)制

       分析函數(shù)是在整個SQL查詢結(jié)束后(SQL語句中的order by 的執(zhí)行比較特殊)再進(jìn)行的操作，也就是說SQL語句中的order by也會影響分析函數(shù)的執(zhí)行結(jié)果：

  • 兩者一致：如果SQL語句中的order by 滿足分析函數(shù)分析時要求的排序，那么SQL語句中的排序?qū)⑾葓?zhí)行，分析函數(shù)在分析時就不必再排序。
  • 兩者不一致：如果SQL語句中的order by 不滿足分析函數(shù)分析時要求的排序，那么SQL語句中的排序?qū)⒆詈笤诜治龊瘮?shù)分析結(jié)束后執(zhí)行排序。

2.2 分析函數(shù)中的分組、排序、窗口

       分析函數(shù)包含三個分析子句：分組(partition by)、排序(order by)、窗口(rows)。

       窗口就是分析函數(shù)分析時要處理的數(shù)據(jù)范圍，就拿sum來說，它是sum窗口中的記錄而不是整個分組中的記錄。因此我們在想得到某個欄位的累計值時，我們需要把窗口指定到該分組中的第一行數(shù)據(jù)到當(dāng)前行，如果你指定該窗口從該分組中的第一行到最后一行，那么該組中的每一個sum值都會一樣，即整個組的總和。

窗口子句中我們經(jīng)常用到指定第一行，當(dāng)前行，最后一行這樣的三個屬性：

  • 第一行是       unbounded preceding
  • 當(dāng)前行是       current row
  • 最后一行是    unbounded following

窗口子句不能單獨(dú)出現(xiàn)，必須有order by 子句時才能出現(xiàn)，如：

LAST_VALUE(SAL) OVER (PARTITION BY DEPTNO ORDER BY SAL ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING )

以上示例指定窗口為整個分組.

而出現(xiàn)order by 子句的時候，不一定要有窗口子句，但效果會不一樣，此時窗口默認(rèn)是當(dāng)前組的第一行到當(dāng)前行！

SQL語句為：

SELECT DEPTNO, EMPNO, ENAME, SAL,
last_value(SAL) OVER(PARTITION BY DEPTNO ORDER BY SAL) MAX_SAL FROM EMP;

等價于

SELECT DEPTNO, EMPNO, ENAME, SAL,last_value(SAL) OVER(PARTITION BY DEPTNO 
ORDER BY SAL ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) MAX_SAL FROM EMP;

結(jié)果如下圖所示：

當(dāng)省略窗口子句時：

  • 如果存在order by, 則默認(rèn)的窗口是 unbounded preceding and current row.
  • 如果同時省略order by, 則默認(rèn)的窗口是 unbounded preceding and unbounded following.

如果省略分組，則把全部記錄當(dāng)成一個組：

  • 如果存在order by 則默認(rèn)窗口是unbounded preceding and current row
  • 如果這時省略order by 則窗口默認(rèn)為 unbounded preceding and unbounded following

2.3 幫助理解over()的實(shí)例

例1：關(guān)注點(diǎn)：SQL無排序，over()排序子句省略

select deptno, empno, ename, sal, last_value(sal) over(partition by deptno) from emp;

例2：關(guān)注點(diǎn)：SQL無排序，over()排序子句有，窗口省略

select deptno, empno, ename, sal, last_value(sal) over(partition by deptno 
order by sal desc) from emp;

例3：關(guān)注點(diǎn)：SQL無排序，over()排序子句有，窗口也有，窗口特意強(qiáng)調(diào)全組數(shù)據(jù)

select deptno, empno, ename, sal, last_value(sal) over(partition by deptno 
order by sal rows between unbounded preceding and unbounded following) max_sal 
from emp;

例4：關(guān)注點(diǎn)：SQL有排序（正序），over() 排序子句無，先做SQL排序再進(jìn)行分析函數(shù)運(yùn)算

select deptno, mgr, ename, sal, hiredate, last_value(sal) over(partition by deptno)
last_value from emp where deptno=30 order by deptno, mgr;

例5：關(guān)注點(diǎn)：SQL有排序（倒序），over() 排序子句無，先做SQL排序再進(jìn)行分析函數(shù)運(yùn)算

select deptno, mgr, ename, sal, hiredate, last_value(sal) over(partition by deptno)
last_value from emp where deptno=30 order by deptno, mgr desc;

例6：關(guān)注點(diǎn)：SQL有排序（倒序），over()排序子句有，窗口子句無，此時的運(yùn)算是：SQL先選數(shù)據(jù)但是不排序，而后排序子句先排序并進(jìn)行分析函數(shù)處理（窗口默認(rèn)為第一行到當(dāng)前行），最后再進(jìn)行SQL排序

select deptno, mgr, ename, sal, hiredate, min(sal) over(partition by deptno 
order by sal)last_value from emp where deptno=30 order by deptno, mgr desc;

select deptno, mgr, ename, sal, hiredate, min(sal) over(partition by deptno 
order by sal desc) last_value from emp where deptno=30 order by deptno, mgr desc;

3. 常見分析函數(shù)

3.1 演示表和數(shù)據(jù)的生成

建表語句：

create table t(
 BILL_MONTH VARCHAR2(12),
 AREA_CODE NUMBER,
 NET_TYPE VARCHAR(2),
 LOCAL_FARE NUMBER
);

插入數(shù)據(jù)：

insert into t values('200405',5761,'G', 7393344.04);
insert into t values('200405',5761,'J', 5667089.85);
insert into t values('200405',5762,'G', 6315075.96);
insert into t values('200405',5762,'J', 6328716.15);
insert into t values('200405',5763,'G', 8861742.59);
insert into t values('200405',5763,'J', 7788036.32);
insert into t values('200405',5764,'G', 6028670.45);
insert into t values('200405',5764,'J', 6459121.49);
insert into t values('200405',5765,'G', 13156065.77);
insert into t values('200405',5765,'J', 11901671.70);
insert into t values('200406',5761,'G', 7614587.96);
insert into t values('200406',5761,'J', 5704343.05);
insert into t values('200406',5762,'G', 6556992.60);
insert into t values('200406',5762,'J', 6238068.05);
insert into t values('200406',5763,'G', 9130055.46);
insert into t values('200406',5763,'J', 7990460.25);
insert into t values('200406',5764,'G', 6387706.01);
insert into t values('200406',5764,'J', 6907481.66);
insert into t values('200406',5765,'G', 13562968.81);
insert into t values('200406',5765,'J', 12495492.50);
insert into t values('200407',5761,'G', 7987050.65);
insert into t values('200407',5761,'J', 5723215.28);
insert into t values('200407',5762,'G', 6833096.68);
insert into t values('200407',5762,'J', 6391201.44);
insert into t values('200407',5763,'G', 9410815.91);
insert into t values('200407',5763,'J', 8076677.41);
insert into t values('200407',5764,'G', 6456433.23);
insert into t values('200407',5764,'J', 6987660.53);
insert into t values('200407',5765,'G', 14000101.20);
insert into t values('200407',5765,'J', 12301780.20);
insert into t values('200408',5761,'G', 8085170.84);
insert into t values('200408',5761,'J', 6050611.37);
insert into t values('200408',5762,'G', 6854584.22);
insert into t values('200408',5762,'J', 6521884.50);
insert into t values('200408',5763,'G', 9468707.65);
insert into t values('200408',5763,'J', 8460049.43);
insert into t values('200408',5764,'G', 6587559.23);
insert into t values('200408',5764,'J', 7342135.86);
insert into t values('200408',5765,'G', 14450586.63);
insert into t values('200408',5765,'J', 12680052.38);
commit;

3.2 first_value()與last_value():求最值對應(yīng)的其他屬性

問題：取出每個月通話費(fèi)最高和最低的兩個地區(qū)

思路：先進(jìn)行g(shù)roup by bill_month, area_code使用聚合函數(shù)sum()求解出by bill_month, area_code的local_fare總和, 即sum(local_fare), 然后再運(yùn)用分析函數(shù)進(jìn)行求解每個月通話費(fèi)用最高和最低的兩個地區(qū)。

select bill_month, area_code, sum(local_fare) local_fare,
first_value(area_code) over(partition by bill_month order by sum(local_fare) desc rows between unbounded preceding and unbounded following) firstval,
last_value(area_code) over(partition by bill_month order by sum(local_fare) desc rows between unbounded preceding and unbounded following) lastval
from t group by bill_month, area_code;

3.3 rank()、dense_rank()與row_number() 排序問題

演示數(shù)據(jù)再Oracle自帶的scott用戶下

1.rank()值相同時排名相同，其后排名跳躍不連續(xù)

select * from (
select deptno, ename, sal,  rank() over(partition by deptno order by sal desc) rw from emp
) where rw < 4;

 2. dense_rank()值相同時排名相同，其后排名連續(xù)不跳躍

select * from (
select deptno, ename, sal,  dense_rank() over(partition by deptno order by sal desc) rw from emp
) where rw <= 4;

3. row_number()值相同時排名不相等，其后排名連續(xù)不跳躍

select * from (
select deptno, ename, sal,  row_number() over(partition by deptno order by sal desc) rw from emp
) where rw <= 4;

3.4 lag()與lead():求之前或之后的第N行

lag(arg1, arg2, arg3):

  • arg1：是從其他行返回的表達(dá)式
  • arg2：是希望檢索的當(dāng)前行分區(qū)的偏移量。是一個正的偏移量，是一個往回檢索以前的行數(shù)目
  • arg3：是在arg2表示的數(shù)目超出了分組的范圍時返回的值

而lead()與lag()相反

select bill_month, area_code, local_fare cur_local_fare,
lag(local_fare, 1, 0) over(partition by area_code order by bill_month)
last_local_fare,
lead(local_fare, 1, 0) over(partition by area_code order by bill_month) 
next_local_fare
from (select bill_month, area_code, sum(local_fare) local_fare 
                                from t group by bill_month, area_code);

3.5 rollup()與cube()：排列組合分組

group by rollup(A, B, C)：

首先會對 (A, B, C) 進(jìn)行g(shù)roup by,

然后再對 (A, B) 進(jìn)行g(shù)roup by,

其后再對 (A) 進(jìn)行g(shù)roup by,

最后對全表進(jìn)行匯總操作。

group by cube(A, B, C):

則首先會對 (A, B, C) 進(jìn)行g(shù)roup by,

然后依次是 (A, B), (A, C), (A), (B, C), (B), (C),

最后對全表進(jìn)行匯總操作。

1.生成演示數(shù)據(jù)：

create table scott.tt as select * from dba_indexes;

2.普通group by 體驗(yàn)

select owner, index_type, status, count(*) from tt where owner like 'SY%' 
group by owner, index_type, status;

3. group by rollup(A, B, C)：

首先會對 (A, B, C) 進(jìn)行g(shù)roup by,

然后再對 (A, B) 進(jìn)行g(shù)roup by,

其后再對 (A) 進(jìn)行g(shù)roup by,

最后對全表進(jìn)行匯總操作。

select owner, index_type, status, count(*) from tt where owner like 'SY%' 
group by rollup(owner, index_type, status);

4. group by cube(A, B, C):

則首先會對 (A, B, C) 進(jìn)行g(shù)roup by,

然后依次是 (A, B), (A, C), (A), (B, C), (B), (C),

最后對全表進(jìn)行匯總操作。

select owner, index_type, status, count(*) from tt where owner like 'SY%' 
group by cube(owner, index_type, status);

（只截取了部分圖）

3.6 max()、min()、sum()與avg()：求移動的最值、總和與平均值

問題：計算出各個地區(qū)連續(xù)3個月的通話費(fèi)用的平均數(shù)(移動平均值)

select area_code, bill_month, local_fare,
sum(local_fare) over(partition by area_code order by to_number(bill_month) 
                    range between 1 preceding and 1 following) month3_sum,
avg(local_fare) over(partition by area_code order by to_number(bill_month) 
                    range between 1 preceding and 1 following) month3_avg,
max(local_fare) over(partition by area_code order by to_number(bill_month) 
                    range between 1 preceding and 1 following) month3_max,
min(local_fare) over(partition by area_code order by to_number(bill_month) 
                    range between 1 preceding and 1 following) month3_min
from (select bill_month, area_code, sum(local_fare) local_fare from t 
                                          group by area_code, bill_month);

問題：求各地區(qū)按月份累加的通話費(fèi)

select area_code, bill_month, local_fare, sum(local_fare) over(partition by area_code 
order by bill_month asc) last_sum_value
from(select area_code, bill_month, sum(local_fare) local_fare from t 
group by area_code, bill_month) order by area_code, bill_month;

3.7 ratio_to_report()：求百分比

問題：求各地區(qū)花費(fèi)占各月花費(fèi)的比例

select bill_month, area_code, sum(local_fare) local_fare,
RATIO_TO_REPORT(sum(local_fare)) OVER (partition by bill_month) AS area_pct
from t group by bill_month, area_code;

總結(jié)

到此這篇關(guān)于Oracle常見分析函數(shù)的文章就介紹到這了,更多相關(guān)Oracle分析函數(shù)內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

相關(guān)文章

最新評論