你可以使用 case 表达式：

select
    customer_name,
    case when customer_name_modified is null or customer_name_modified = '' 
        then customer_name 
        else customer_name_modified 
    end customer_name_modified 
from mytable

如果你在找一个 update 声明：

update mytable
set customer_name_modified = customer_name
where customer_name_modified is null or customer_name_modified = ''