脏读又称无效数据的读出,是指在数据库访问中,事务T1将某一值修改,然后事务T2读取该值,此后T1因为某种原因撤销对该值的修改,这就导致了T2所读取到的数据是无效的,值得注意的是,脏读一般是针对于update操作的。
... 8) PROPAGATION_NESTED 与PROPAGATION_REQUIRES_NEW的区别 i. Dirty Reads 脏读 ii. Non-Repeatable Reads 不可重复读 ...
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脏读:A 1检索a 2未提交的数据。
理想情况下,多个线程不能同时访问同一块数据,脏读将不复存在,死锁则会被自动监测和处理。
Ideally no two threads can try to modify the same piece of data at the same time, dirty reads are not possible, and deadlocks are automatically detected and handled.
SQL 2005有一个 基于快照的隔离级别 ,它能在不允许“脏读”的情况下避免数据读取阻塞数据写入,或者数据写入阻塞数据读取。
SQL 2005 has snapshot-based isolation levels that prevent readers from blocking writers or writers from blocking readers without allowing dirty reads.
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