事务处理问题，急

Question

T1           time           T2
------------------------------
BT            1
sum=0         2
read（x）      3
read（Y）      4
sum:=sum+x    5  
sum:=sum+y    6    
              7        BT
              8        read(z)
              9        z= z -10
             10        write(z)
              11       read(x)
              12       x = x +10
              13       wirte（x)
              14       commit
read(z)       15
sum =sum +z   16
commit        17
BT 是begin transaction.
问 sum是多少，

Answer 1

个人认为sum=x+y+z-10;
x,y,z 均为1时间前的值