Mysql事务隔离级别之读提交
查看mysql 事务隔离级别
mysql> show variables like '%isolation%';
+---------------+----------------+
| Variable_name | Value |
+---------------+----------------+
| tx_isolation | READ-COMMITTED |
+---------------+----------------+
1 row in set (0.00 sec)
可以看到当前的事务隔离级别为 READ-COMMITTED 读提交
下面看看当前隔离级别下的事务隔离详情，开启两个查询终端A、B。
下面有一个order表，初始数据如下
mysql> select * from `order`;
+----+--------+
| id | number |
+----+--------+
| 13 | 1 |
+----+--------+
1 row in set (0.00 sec)第一步，在A,B中都开启事务
mysql> start transaction;
Query OK, 0 rows affected (0.00 sec)第二步查询两个终端中的number值
- A
mysql> select * from `order`;
+----+--------+
| id | number |
+----+--------+
| 13 | 1 |
+----+--------+
1 row in set (0.00 sec)- B
mysql> select * from `order`;
+----+--------+
| id | number |
+----+--------+
| 13 | 1 |
+----+--------+
1 row in set (0.00 sec)第三步将B中的number修改为2,但不提交事务
mysql> update `order` set number=2;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0第四步查询A中的值
mysql> select * from `order`;
+----+--------+
| id | number |
+----+--------+
| 13 | 1 |
+----+--------+
1 row in set (0.00 sec)发现A中的值并没有修改。
第五步，提交事务B,再次查询A中的值
- B
mysql> commit;
Query OK, 0 rows affected (0.01 sec)- A
mysql> select * from `order`;
+----+--------+
| id | number |
+----+--------+
| 13 | 2 |
+----+--------+
1 row in set (0.00 sec)发现A中的值已经更改
第六步，提交A中的事务，再次查询A，B的值。
- A
mysql> commit;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from `order`;
+----+--------+
| id | number |
+----+--------+
| 13 | 2 |
+----+--------+
1 row in set (0.00 sec)- B
mysql> select * from `order`;
+----+--------+
| id | number |
+----+--------+
| 13 | 2 |
+----+--------+
1 row in set (0.00 sec)发现A,B中的值都更改为2了。
下面给一个简单的示意图
