查询在PostgreSQL中给出除零错误

我试图运行以下查询,结果我postgres错误：除零

select 
    request_count,response_count,(response_count*100) / (request_count+response_count) AS proportion 
from total_dummy_table;

如何通过零错误避免和解决除法？

尝试使用以下查询修复,但获得与上面相同的结果

SELECT 
    request_count,(response_count*100) / (request_count) AS proportion 
FROM 
    total_dummy_table
ORDER BY 
    (response_count*100) /(CASE request_count WHEN 0 Then NULL ELSE request_count END) DESC NULLS FirsT

请告诉我我在哪里做错了,或者我该如何解决这个问题.
谢谢！

结果期望：

查询应该返回如下所示的内容：

Request_count | Response_count | Proportion

1603423       |  585706        | 36.52

快速注释：表total_dummy_table没有列名称比例,它是结果中添加的计算比例.

select request_count,case 
    when 
    request_count+response_count = 0 then 0 
    else
(response_count*100) / (request_count+response_count) 
end AS proportion 
from total_dummy_table;