mysql5.x和mysql8.x查看和设置隔离级别

MySQL的隔离级别

级别	标志	值	描述
读未提交	READ-UNCOMMITTED	0	存在脏读、不可重复读、幻读的问题
读已提交	READ-COMMITTED	1	解决脏读的问题，存在不可重复读、幻读的问题
可重复读	REPEATABLE-READ	2	mysql 默认级别，解决脏读、不可重复读的问题，存在幻读的问题
序列化	SERIALIZABLE	3	解决脏读、不可重复读、幻读，可保证事务安全，但完全串行执行，性能最低

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我们可以通过以下命令查看/设置全局/会话的事务隔离级别

mysql5.x

SELECT @@global.tx_isolation, @@tx_isolation;

one.PNG

mysql8.x

SELECT @@global.transaction_isolation, @@transaction_isolation;

two.PNG

mysql5.x修改回话隔离级别（才可以操作数据表的）

SET tx_isolation = 0;
set  @@session.tx_isolation = 0;
SET tx_isolation = 'READ-UNCOMMITTED';
set  @@session.tx_isolation = 'READ-UNCOMMITTED';SET tx_isolation = 1;
set  @@session.tx_isolation = 1;
SET tx_isolation = 'READ-COMMITTED';
set  @@session.tx_isolation = 'READ-COMMITTED';SET tx_isolation = 2;
set  @@session.tx_isolation = 2;
SET tx_isolation = 'REPEATABLE-READ';
set  @@session.tx_isolation = 'REPEATABLE-READ';SET tx_isolation = 3;
set  @@session.tx_isolation = 3;
SET tx_isolation = 'SERIALIZABLE';
set  @@session.tx_isolation = 'SERIALIZABLE';

mysql8.x修改回话隔离级别（才可以操作数据表的）

SET transaction_isolation = 0;
set  @@session.transaction_isolation = 0;
SET transaction_isolation = 'READ-UNCOMMITTED';
set  @@session.transaction_isolation = 'READ-UNCOMMITTED';SET transaction_isolation = 1;
set  @@session.transaction_isolation = 1;
SET transaction_isolation = 'READ-COMMITTED';
set  @@session.transaction_isolation  = 'READ-COMMITTED';SET transaction_isolation = 2;
set  @@session.transaction_isolation = 2;
SET transaction_isolation = 'REPEATABLE-READ';
set  @@session.transaction_isolation = 'REPEATABLE-READ';SET transaction_isolation = 3;
set  @@session.transaction_isolation = 3;
SET transaction_isolation = 'SERIALIZABLE';
set  @@session.transaction_isolation = 'SERIALIZABLE';