要計算百分比值

Question

我有如下數據..

count    ID 
---------------------- 
10     1 
20     2 
30     4 

我如何能實現第三列，它計算在oracle中的百分比。

count    ID % 
------------------------------------- 
10     1 10/(10+20+30) 
20     2 20/(10+20+30) 
30     4 30/(10+20+30) 

Answer 1

SELECT id, count, (count/(SELECT SUM(count) FROM table) * 100) as per FROM table GROUP BY id 

Answer 2

使用RATIO_TO_REPORT

SQL Fiddle

查詢：

with your_table(count_, id_) as (
    select 10,1 from dual union all 
    select 20,2 from dual union all 
    select 30,4 from dual 
) 
select count_, id_, 
ratio_to_report(count_) over() as percentage 
from your_table 

Results：

| COUNT_ | ID_ |   PERCENTAGE | 
|--------|-----|---------------------| 
|  10 | 1 | 0.16666666666666666 | 
|  20 | 2 | 0.3333333333333333 | 
|  30 | 4 |     0.5 | 

Answer 3

窗口函數爲這類問題提供了最佳解決方案。您試圖實現的是在表的一個查詢中進行兩級聚合。

select id 
     ,count(*) 
     ,sum(count(*)) over() as CountOfAll 
     ,(1.0 * count(*))/sum(count(*)) over() as Pct 
from some_table 
group by id 

在情況下，分母可能導致零，你必須包裝在一個CASE語句的PCT計算零個誤差，避免分裂：

select id 
    ,count(*) 
    ,sum(count(*)) over() as CountOfAll 
    ,case when sum(count(*)) over() = 0 
     then 0 
     else (1.0 * count(*))/sum(count(*)) over() 
    end as Pct 
from some_table 
group by id 

窗口功能開闢了很多在單個查詢中創建聚合結果的可能性，並且是添加到SQL工具帶的有用工具！