问题
单项选择题
There is an hour to go. Could we sit somewhere to have a drink?（）
A.Have a try.
B.Sure.
C.Don‘t go, please.
D.No, thanks.
答案
参考答案：B
搜题请搜索小程序“爱下问搜题”
There is an hour to go. Could we sit somewhere to have a drink?（）
A.Have a try.
B.Sure.
C.Don‘t go, please.
D.No, thanks.
参考答案：B
设有两个事务T1和T2，其并发操作序列如下表所示。下列说法中正确的是
| 步骤 | T1 | T2 |
| 1 | 读A=100 | |
| 2 | A=A*2写图 | |
| 3 | 读A=200 | |
| 4 | ROLLBACK |
A．该操作序列不存在问题
B．该操作序列丢失修改
C．该操作序列不能重复读
D．该操作序列读出"脏"数据
