mysql 查询会加锁开启事务吗? - V2EX
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noble4cc
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mysql 查询会加锁开启事务吗?

  •  
  •   noble4cc 2020-05-10 19:28:12 +08:00 4174 次点击
    这是一个创建于 2053 天前的主题,其中的信息可能已经有所发展或是发生改变。

    不主动加锁比如 for update 也会开启事务并对查询的事务加锁吗?

    4 条回复    2020-05-19 16:04:26 +08:00
    xizismile
        1
    xizismile  
       2020-05-10 20:17:22 +08:00 via Android   1
    mysql 读分为两种,锁读和一致性读

    锁读(共享读( select in share mode )和排它读( select for update ))会加锁
    一致性读(普通的那种读)不加锁

    开启还是不开启事务,这和应用端事务设置以及数据库事务设置都有关系
    gaius
        2
    gaius  
       2020-05-10 22:37:35 +08:00 via Android
    事务是事务,锁是锁
    billlee
        3
    billlee  
       2020-05-10 22:56:04 +08:00
    不执行 START TRANSACTION 的情况下,是否开启事务由连接的 autocommit 配置决定。
    默认隔离级别下,开启事务时执行单纯的 SELECT 不会加锁,会通过 MVCC 实现 Repeatable read
    Coolha
        4
    Coolha  
       2020-05-19 16:04:26 +08:00
    不使用 for update 读,不加锁,隔离性靠 MVCC 机制保证
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