另一种选择是使用解析函数的窗口子句

with my_data as (
  select 1 as month, 'A' as product, 10 as sales from dual union all
  select 1 as month, 'B' as product, 12 as sales from dual union all
  select 1 as month, 'C' as product, 17 as sales from dual union all
  select 2 as month, 'A' as product, 21 as sales from dual union all
  select 3 as month, 'C' as product, 2 as sales from dual union all
  select 3 as month, 'B' as product, 21 as sales from dual union all
  select 4 as month, 'B' as product, 23 as sales from dual 
)
select 
  month, 
  product, 
  sales,
  nvl(sum(sales) 
    over (partition by product order by month 
          range between 3 preceding and 1 preceding),0)/3 as average_sales
from my_data
order by month, product

字符串

SELECT month, 
       productType, 
       sales,
       (lag(sales, 3) over (partition by produtType order by month) +
        lag(sales, 2) over (partition by productType order by month) + 
        lag(sales, 1) over (partition by productType order by month))/3 moving_avg
  FROM your_table_name

字符串
--已编辑以添加缺少的右括号