sqlserver 事务级别

发布时间：2020-12-12 12:59:50 所属栏目：MsSql教程来源：网络整理

导读：?? 1. Read Uncommitted?指定语句可以读取已由其他事务修改但尚未提交的行. 最低等级的事务隔离，仅仅保证了读取过程中不会读取到非法数据. [csharp] view plain copy print ? conn.BeginTransaction(IsolationLevel.ReadUncommitted)?? conn.BeginTransacti

1.Read Uncommitted?指定语句可以读取已由其他事务修改但尚未提交的行.最低等级的事务隔离，仅仅保证了读取过程中不会读取到非法数据.

[csharp] view plain copy print ?

conn.BeginTransaction(IsolationLevel.ReadUncommitted)??

conn.BeginTransaction(IsolationLevel.ReadUncommitted)

[sql] view plain copy print ?

命令:??
SET?TRANSACTION?ISOLATION?LEVEL?Read?Uncommitted???

命令:
SET TRANSACTION ISOLATION LEVEL Read Uncommitted

2.Read Committed：大多数主流数据库的默认事务等级，保证了一个事务不会读到另一个并行事务已修改但未提交的数据，避免了“脏读取”

[csharp] view plain copy print ?

conn.BeginTransaction(IsolationLevel.ReadCommitted)??

conn.BeginTransaction(IsolationLevel.ReadCommitted)

[sql] view plain copy print ?

SET?TRANSACTION?ISOLATION?LEVEL?Read?Committed??

SET TRANSACTION ISOLATION LEVEL Read Committed

3.?Repeatable Read：保证了一个事务不会修改已经由另一个事务读取但未提交（回滚）的数据。避免了“脏读取”和“不可重复读取”的情况，但是带来了更多的性能损失

[csharp] view plain copy print ?

conn.BeginTransaction(IsolationLevel.RepeatableRead)??

conn.BeginTransaction(IsolationLevel.RepeatableRead)

[sql] view plain copy print ?

SET?TRANSACTION?ISOLATION?LEVEL?Repeatable?Read??

SET TRANSACTION ISOLATION LEVEL Repeatable Read

4.Serializable：最高等级的事务隔离，上面3种不确定情况都将被规避。这个级别将模拟事务的串行执行。

[csharp] view plain copy print ?

conn.BeginTransaction(IsolationLevel.Serializable)??

conn.BeginTransaction(IsolationLevel.Serializable)

[sql] view plain copy print ?

SET?TRANSACTION?ISOLATION?LEVEL?Serializable???

SET TRANSACTION ISOLATION LEVEL Serializable

（编辑：李大同）

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