select @@tx_isolation; //查看隔离级别 
set session transaction isolation level read uncommitted; //设置读未提交级别 
start transaction; //打开事务 
rollback; //回滚 
commit; //提交 
set session transaction isolation level read committed; //设置读提交级别 
set session transaction isolation level repeatable read; //设置可重复读（缺省），保证每次读的结果是一样的 
set session transaction isolation level serializable; //设置成序列化

MySQL 数据库事物隔离级别的设置