学号 | 课程号 | 分数 |
S1 | C1 | 80 |
S1 | C2 | 75 |
S2 | C1 | null |
S2 | C2 | 55 |
S3 | C3 | 90 |
| 事务T1 | 事务T2 |
1 | 读C=100,C=C*2,写回C=200 | |
2 | | 读C=200 |
3 | ROLLBACK TRAN,C恢复为100 | (错误的C值已读出) |
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