如何为特定类别的每月总销售额添加条件

How can I add condition for total sales per month for specific category

假设有一个table如下结构

select Year, Month , customer, Category, Amount 
from claim

我想为每个月应用折扣,如 table(绿色列)所示:

其他月份和客户也是如此。

是否可以在 SQL 中使用子查询或一些可以提供帮助的函数来做到这一点?

请指教

可以使用case .. when语句和解析函数如下:

select Year, Month , customer, Category, Amount,
       Case when category = 'Brand'
            then
              Case when total_sales > 15000 then '2%'
                   When total_sales > 20000 then '3%'
              End
       End as disc,
       Case when category = 'Brand' 
            then
              Case when total_sales > 15000 then 2*amount/100
                   When total_sales > 20000 then 3*amount/100
              End
       End disc_amount
From
(select Year, Month , customer, Category, Amount,
        sum(case when category in ('Brand', 'Generic') then amount else 0 end)
          over (partition by year, month, customer) as total_sales
 from claim)