图81三种数据不一致性 ①读A=16 读A=16 ③A←A-1 写回 A=15 A←A-1 写回A=15 (a)丢失修改 An Introduction to Database SystemAn Introduction to Database System 图8.1 三种数据不一致性 T1 T2 ① 读A=16 ② ③ A←A-1 写回 A=15 ④ 读A=16 A←A-1 写回A=15 (a) 丢失修改