数据库事务处理之排他锁

下面做作一个实验，验证锁的效果

终端一,首先进入事务状态然后运行下面语句

		
mysql> begin;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from t1 where id='3' for update;
+----+--------+---------------------+---------------------+
| id | name   | ctime               | mtime               |
+----+--------+---------------------+---------------------+
|  3 | test   | 0000-00-00 00:00:00 | 2013-01-14 13:05:41 |
+----+--------+---------------------+---------------------+
1 row in set (0.00 sec)
		
		

终端二, 查询表中数据

		
mysql> select * from t1;
+----+--------+---------------------+---------------------+
| id | name   | ctime               | mtime               |
+----+--------+---------------------+---------------------+
|  1 | neo    | 0000-00-00 00:00:00 | 2013-01-14 13:00:00 |
|  2 | zen    | 0000-00-00 00:00:00 | 2013-01-14 13:00:43 |
|  3 | test   | 0000-00-00 00:00:00 | 2013-01-14 13:05:41 |
+----+--------+---------------------+---------------------+
3 rows in set (0.00 sec)
		
		

增加“for update”查询非锁定记录

		
mysql> select * from t1 where id=2 for update;
+----+------+---------------------+---------------------+
| id | name | ctime               | mtime               |
+----+------+---------------------+---------------------+
|  2 | zen  | 0000-00-00 00:00:00 | 2013-01-14 13:00:43 |
+----+------+---------------------+---------------------+
1 row in set (0.00 sec)
		
		

查询被锁定记录

		
mysql> select * from t1 where id=3 for update;
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction
		
		

查询所有记录，因为记录中包含了id=3那条，所以也不允许查询。

		
mysql> select * from t1 for update;
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction
		
		

测试修改记录

		
mysql> UPDATE `t1` SET `name`='testaa' WHERE  `id`=3;
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction