目录
一.自己的理解
二.网上的总结
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 /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 | |