您可以使用ln和exp函数将乘法转换为加法，反之亦然。但是它会增加一些舍入误差，如果乘数的数量很大或它们的值太稀疏，则可能会很明显。

select
  item,
  round(exp(sum(ln(1 - PERCENTAGE/100))), 5) as mult
from sample
group by item

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或者使用model clause执行逐行迭代，而不使用ln/exp时出现的近似。

with calc as (
  select *
  from sample
  model
    partition by (item)
    dimension by (row_number() over(partition by item order by null) as dim)
    measures (PERCENTAGE as mult, 0 as last_row)
    rules update (
      mult[any] order by dim = coalesce(mult[cv() - 1], 1)*(1 - mult[cv()]/100),
      /*Last row indicator that will contain aggregated value*/
      last_row[any] = decode(last_row[cv()+1], null, 1, 0)
    )
)
select
  item,
  mult
from calc
where last_row = 1

型
或者定义本地PL/SQL函数，该函数将遍历乘数集合并执行乘法。然后将其应用于collect聚合函数的结果。Oracle为table of number预定义了sys.ODCINumberList类型。

with function f_mult(nums sys.odcinumberlist)
  return number
as
  pragma udf;
  mult number := 1;
begin
  for i in 1..nums.count() loop
    mult := mult * (1 - nums(i)/100);
  end loop;
  return mult;
end;

select
  item,
  f_mult(cast(collect(PERCENTAGE) as sys.odcinumberlist)) as agg
from sample
group by item

型
对于您的示例数据：

create table sample(ITEM, PERCENTAGE) as
select 'MOBILE', 2 from dual union all
select 'MOBILE', 5 from dual union all
select 'TABLET', 5 from dual union all
select 'TABLET', 3 from dual

型
所有上述查询返回相同的结果：
| 项目|AGG|
| --|--|
| 移动的|点九三一口径|
| 平板|.9215|
fiddle的

由于项目是成对出现的，一种选择是使用lead解析函数并计算两个值：
样本数据：

SQL> with test (item, percentage) as
  2    (select 'mobile', 2 from dual union all
  3     select 'mobile', 5 from dual union all
  4     select 'tablet', 5 from dual union all
  5     select 'tablet', 3 from dual
  6    ),

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查询：

7  temp as
  8    (select item,
  9            percentage / 100 pct,
 10            lead(percentage/100) over (partition by item order by null) pct2
 11     from test
 12    )
 13  select item,
 14         (1 - pct) * (1 - pct2) percentage
 15  from temp
 16  where pct2 is not null;

ITEM   PERCENTAGE
------ ----------
mobile       ,931
tablet      ,9215

SQL>

型

这是一种使用解析函数FIRST_VALUE和LAST_VALUE的方法：

with cte as (
  select ITEM, ( 1 - FIRST_VALUE(percentage) over (partition by item)/100) 
             * ( 1 - LAST_VALUE(percentage) over (partition by item)/100) as PERCENTAGE,
         row_number() over (partition by item order by null) as rn
  from mytable
)
select ITEM, PERCENTAGE
from cte
where rn = 1

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Demo here