从特定记录开始更改所有记录的总和

Question

我有桌子：

+-------------+------------+---------+  
| Code        | Num        | Total   |  
+-------------+------------+---------+  
| A           | 5          | 10      |  
+-------------+------------+---------+    
| B           | 7          | 17      |  
+-------------+------------+---------+  
| C           | 8          | 25      |  
+-------------+------------+---------+  

现在，如果我想将记录B的Num值从7改为9而不是记录B的总值 是9和记录C 27.如何编写将从特定记录开始更改所有总和的查询？

Answer 1

工作小提琴：http://sqlfiddle.com/#!2/41cb1/1/0

create table b as 
(Select 'A' as code,5 as num ,10 as total)
UNION
(Select 'B' as code,7 as num ,17 as total)
UNION
(Select 'C' as code,8 as num ,25 as total);

update b set num = 9 where code = 'B';
set @var=5;
Update b 
INNER JOIN 
(Select code, num, b.total, @var:=@var+num as NewTotal from b order by code) c
on c.Code=B.code
set b.total=NewTotal;


select * from b;