第十四章事务控制和锁定语句

刺骨的言语ヽ痛彻心扉 2023-07-06 14:33 10阅读 0赞

简介：

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**mysql 对不同的存储引擎 支持的锁定级别不一样，最常用的innodb 存储引擎 支持行级别锁定：**

**具体每种存储引擎 事务安全，支持的索引类型，以及空间使用，速度等 区别 参考下图：**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Jvc3Nfd2F5_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Jvc3Nfd2F5_size_16_color_FFFFFF_t_70 2][]

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**一般情况下 主动干预事务的情况比较少。自动锁 通过设置合理的 锁 和设置合理的 等待时间 可以满足大部分业务需要**

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**简单的 事务开启和提交:**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Jvc3Nfd2F5_size_16_color_FFFFFF_t_70 5][]

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**注意的是 使用start transaction 命令开启一个新事务的时候，或隐含的 执行一个 unlock tables ；**

**如下图示例：**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Jvc3Nfd2F5_size_16_color_FFFFFF_t_70 8][]

**回滚操作可以设置多个回滚点，便于根据不同业务回滚到不同位置。**![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Jvc3Nfd2F5_size_16_color_FFFFFF_t_70 9][]

事务回滚点示例：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Jvc3Nfd2F5_size_16_color_FFFFFF_t_70 10][]

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**分布式事务，只支持innodb 存储引擎**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Jvc3Nfd2F5_size_16_color_FFFFFF_t_70 12][]

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