--> 测试数据：[tb]
IF OBJECT_ID('[tb]') IS NOT NULL DROP TABLE [tb]
GO 
CREATE TABLE [tb]([a] INT,[b] INT,[c] INT)
INSERT [tb]
SELECT 1,10,NULL UNION ALL
SELECT 2,1,NULL UNION ALL
SELECT 3,2,NULL UNION ALL
SELECT 4,1,100
--------------开始查询--------------------------
--1
SELECT [a],[b],[c]=100+ISNULL((SELECT SUM([b]) FROM [tb] WHERE [a]>t.[a]),0) FROM [tb] AS t
--2
SELECT [a],[b],[c]=app.[c]+ISNULL((SELECT SUM([b]) FROM [tb] WHERE [a]>t.[a]),0) FROM [tb] AS t
CROSS APPLY(SELECT TOP 1 ISNULL([c],0) AS [c] FROM [tb] ORDER BY [a] DESC ) app
----------------结果----------------------------
/* 
a    b    c
1    10    104
2    1    103
3    2    101
4    1    100
*/

------解决方案--------------------
SQL code

create table hb
(a int,b int,c int)

insert into hb  
select 1, 10, null union all
select 2, 1, null union all
select 3, 2, null union all
select 4, 1, 100


 declare @sql varchar(6000)
 select @sql='
 update t1
 set t1.c=
    (select t2.c+t2.b 
     from hb t2 
     where t2.a=t1.a+1)
 from hb t1
 where t1.c is null'
 exec(@sql)
 while @@rowcount>0
   exec(@sql)

-- 结果
select * from hb

/*
a           b           c
----------- ----------- -----------
1           10          104
2           1           103
3           2           101
4           1           100

(4 row(s) affected)
*/