它取决于您的数据库，也取决于您的“特定规则”，但为了让您开始使用，下面的内容将在SQLServer和其他可能的应用程序中工作。
要将销售订单（so）的所有收入平均分摊到该销售订单的所有行（行），请执行以下操作：

update tbl
set Alloc = new_alloc
from
(select 
   so, 
   line, 
   (sum(contracted) over (partition by so))/
     (count(line) over (partition by so)) as new_alloc
 from tbl) as sub
 where sub.so = tbl.so
   and sub.line = tbl.lineenter code here

要根据行描述应用自定义规则（在本例中，80%为“软件”，20%为“维护”）：

update tbl
set Alloc = new_alloc
from
(select 
   so, 
   line, 
   case when line_description = 'Software' then 0.8 
        when line_description = 'Maintenance' then 0.2 
        end *
     sum(contracted) over (partition by so) as new_alloc
 from tbl) as sub
 where sub.so = tbl.so
   and sub.line = tbl.line

sql小提琴