标签：不能 ctrl specified 另一个 rom database use tab bsp
1、lock tables table1 read,table2 read,table3 read
igoodful@a8-apple-iphone-db00.wh(glc) > show tables; +---------------+ | Tables_in_glc | +---------------+ | mobile | | user | +---------------+ 2 rows in set (0.00 sec) Fri Dec 20 17:42:35 2019 igoodful@a8-apple-iphone-db00.wh(glc) > show open tables where in_use >=1; +----------+-------+--------+-------------+ | Database | Table | In_use | Name_locked | +----------+-------+--------+-------------+ | glc | user | 1 | 0 | +----------+-------+--------+-------------+ 1 row in set (0.00 sec) Fri Dec 20 17:42:47 2019 igoodful@a8-apple-iphone-db00.wh(glc) > lock tables user read; ######### 添加读锁 Query OK, 0 rows affected (0.00 sec) Fri Dec 20 17:43:03 2019 igoodful@a8-apple-iphone-db00.wh(glc) > show open tables where in_use >=1; ########## 表明：添加表读锁后，表被用次数加一 +----------+-------+--------+-------------+ | Database | Table | In_use | Name_locked | +----------+-------+--------+-------------+ | glc | user | 2 | 0 | +----------+-------+--------+-------------+ 1 row in set (0.00 sec) Fri Dec 20 17:43:08 2019 igoodful@a8-apple-iphone-db00.wh(glc) > select * from user; ########## 表明：可以读取锁住的表的数据。 +------+------+ | id | name | +------+------+ | 1 | 1 | | 2 | 1 | +------+------+ 2 rows in set (0.01 sec) Fri Dec 20 17:43:37 2019 igoodful@a8-apple-iphone-db00.wh(glc) > select * from mobile; ########## 表明：只能读取锁住的表的数据，不能查看没有锁住的表的数据 ERROR 1100 (HY000): Table ‘mobile‘ was not locked with LOCK TABLES Fri Dec 20 17:44:11 2019 igoodful@a8-apple-iphone-db00.wh(glc) >
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在另一个会话线程中执行如下语句：
igoodful@a8-apple-iphone-db00.wh(glc) > select * from user; ################# 表明：一个会话给表添加了读锁，那么不影响其他会话线程读取该表数据 +------+------+ | id | name | +------+------+ | 1 | 1 | | 2 | 1 | +------+------+ 2 rows in set (0.00 sec) Fri Dec 20 17:54:11 2019 igoodful@a8-apple-iphone-db00.wh(glc) > insert into user values (3,‘3‘); ################# 表明：一个会话给表添加了读锁，其他会话线程只能对该表进行读取，而不能对该表执行执行dml和ddl语句。 ^CCtrl-C -- sending "KILL QUERY 233531" to server ... Ctrl-C -- query aborted. ERROR 1317 (70100): Query execution was interrupted Fri Dec 20 17:55:59 2019 igoodful@a8-apple-iphone-db00.wh(glc) > select connection_id(); +-----------------+ | connection_id() | +-----------------+ | 233531 | +-----------------+ 1 row in set (0.00 sec) Fri Dec 20 17:57:07 2019 igoodful@a8-apple-iphone-db00.wh(glc) > show open tables where in_use>0;; +----------+-------+--------+-------------+ | Database | Table | In_use | Name_locked | +----------+-------+--------+-------------+ | glc | user | 2 | 0 | +----------+-------+--------+-------------+ 1 row in set (0.00 sec) ERROR: No query specified Fri Dec 20 17:57:25 2019 igoodful@a8-apple-iphone-db00.wh(glc) > lock tables user read; ################# 表明：多个会话线程可以对同一张表添加读锁。 Query OK, 0 rows affected (0.00 sec) Fri Dec 20 17:57:57 2019 igoodful@a8-apple-iphone-db00.wh(glc) >
当一个会话线程执行：
use glc;
lock tables user read;
那么
1）、该会话线程只能查询锁定的这几个表的数据，没有被锁定的表，不能查询到数据
2）、同时阻止其他会话对锁住的表进行事务操作语句和添加write表锁，
3）、其他会话可以对同一个表添加read锁，
4）
执行
标签：不能 ctrl specified 另一个 rom database use tab bsp
原文地址：https://www.cnblogs.com/igoodful/p/12074396.html
