用case when判断，把小于等于当前月份的月份都变为当前月份，然后根据月份汇总就好了

with a as(select distinct substr(dt_date,6,2) as 月份 

from R_TEST5)

select 月份,case when 月份<= '${月份参数}' then '${月份参数}' else 月份 end as 月份

from a

提供个思路，如果每个月份的后面都加一列，如果月份是固定的，就是 2月后面是1加2月的，3月后面是1加2加3月的，如果是扩展出来的， 就是 sum(ds1.select(值，月份<= 参数值 )) ，然后这些列就根据条件属性判断列宽是否为0，月份固定的话，就是固定写参数值 = 几几几  ，扩展的话 ，就判断  参数值 = B1（月份的单元格） 

with a1 as(

select 20 as a,'2022-01' as b

union all

select 30 as a,'2022-02' as b

union all

select 40 as a,'2022-03' as b

union all

select 50 as a,'2022-04' as b

),

b1 as (

select max(b) as b,sum(a) as a from a1 where b<='${参数}'

)

select a1.b,

case when a1.b<='${参数}' then b1.a

     else a1.a

end as new_a

from a1

left join b1 on a1.b=b1.b