查看数据库事务隔离级别

mysql> show variables like 'transaction%';
mysql> select @@transaction_isolation;

修改事务隔离级别的方式

• 由低到高分别为
  • read uncommitted (读未提交)
  • read committed (读提交)
  • repeatable read (重复)
  • Serializable (序列化)

1.只在本次会话有效

mysql> set session transaction isolation level read committed;

2.设置全局的事务隔离级别,该设置不会影响当前已经连接的会话,新会话,将使用新设置的事务隔离级别

mysql> set global transaction isolation level read committed;

3.修改配置文件,重启后生效

[mysqld]
transaction-isolation = REPEATABLE-READ
transaction-read-only = OFF

• Read-Committed(不可重复读)

Transication A	Transication B
begin;	begin;
	-
-
	-
-	commit;
	-

1. 事务A: update ent_stock s set s.count = count-1 where s.name = '库存-1';
2. 事务B: update ent_stock s set s.count = count-1 where s.name = '库存-1';
3. 事务A给库存-1加了X锁,事务B更新时只能阻塞等待事务A提交后才可提交此次更新,反之同理
4. 解决脏读