20.2.2 MySQL表级锁的锁模式

请求锁模式

         是否兼容

当前锁模式

None

读锁

写锁

读锁

是

是

否

写锁

是

否

否

session_1

session_2

获得表film_text的WRITE锁定

mysql> lock table film_text write;

Query OK, 0 rows affected (0.00 sec)

当前session对锁定表的查询、更新、插入操作都可以执行：

mysql> select film_id,title from film_text where film_id = 1001;

+---------+-------------+

| film_id | title       |

+---------+-------------+

| 1001    | Update Test |

+---------+-------------+

1 row in set (0.00 sec)

mysql> insert into film_text (film_id,title) values(1003,'Test');

Query OK, 1 row affected (0.00 sec)

mysql> update film_text set title = 'Test' where film_id = 1001;

Query OK, 1 row affected (0.00 sec)

Rows matched: 1  Changed: 1  Warnings: 0

其他session对锁定表的查询被阻塞，需要等待锁被释放：

mysql> select film_id,title from film_text where film_id = 1001;

等待

释放锁：

mysql> unlock tables;

Query OK, 0 rows affected (0.00 sec)

等待

Session2获得锁，查询返回：

mysql> select film_id,title from film_text where film_id = 1001;

+---------+-------+

| film_id | title |

+---------+-------+

| 1001    | Test  |

+---------+-------+

1 row in set (57.59 sec)