mysql四种隔离级别与实现方式

目录

一.自己的理解

二.网上的总结

 

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一.自己的理解

READ UNCOMMITTED(RU) ： 对于修改的项加排它锁，直到事务结束释放；没有快照读，只能读最新版本的数据。

READ COMMITTED(RC) ：对于修改的项加排它锁，直到事务结束释放；有快照读，快照的粒度是语句级。

REPEATABLE READ(RR) ：对于修改的项加排它锁，直到事务结束释放；有快照读，快照的粒度是事务级。

SERIALIZABLE ： 串行化。

 

二.网上的总结

转自 https://blog.csdn.net/keda8997110/article/details/45080453

InnoDB存储引擎中不同SQL在不同隔离级别下锁比较

隔离级别         一致性读和锁 SQL		Read Uncommited	Read Commited	Repeatable Read	Serializable
SQL	条件
select	相等	None locks	Consisten read/None lock	Consisten read/None lock	Share locks
	范围	None locks	Consisten read/None lock	Consisten read/None lock	Share Next-Key
update	相等	exclusive locks	exclusive locks	exclusive locks	Exclusive locks
	范围	exclusive next-key	exclusive next-key	exclusive next-key	exclusive next-key
Insert	N/A	exclusive locks	exclusive locks	exclusive locks	exclusive locks
replace	无键冲突	exclusive locks	exclusive locks	exclusive locks	exclusive locks
	键冲突	exclusive next-key	exclusive next-key	exclusive next-key	exclusive next-key
delete	相等	exclusive locks	exclusive locks	exclusive locks	exclusive locks
	范围	exclusive next-key	exclusive next-key	exclusive next-key	exclusive next-key
Select ... from ... Lock in share mode	相等	Share locks	Share locks	Share locks	Share locks
	范围	Share locks	Share locks	Share Next-Key	Share Next-Key
Select * from ... For update	相等	exclusive locks	exclusive locks	exclusive locks	exclusive locks
	范围	exclusive locks	Share locks	exclusive next-key	exclusive next-key
Insert into ... Select ... （指源表锁）	innodb_locks_unsafe_for_binlog=off	Share Next-Key	Share Next-Key	Share Next-Key	Share Next-Key
	innodb_locks_unsafe_for_binlog=on	None locks	Consisten read/None lock	Consisten read/None lock	Share Next-Key
create table ... Select ... （指源表锁）	innodb_locks_unsafe_for_binlog=off	Share Next-Key	Share Next-Key	Share Next-Key	Share Next-Key
	innodb_locks_unsafe_for_binlog=on	None locks	Consisten read/None lock	Consisten read/None lock	Share Next-Key