mysql 表级锁之一lock table 1.lock table t1 read: 1.1.当前线程: 读/写当前表/其他表: unlock tables; locktablet1 read;select*fromt1;INSERTINTO`t1` (`c2`, `c3`, `c4`)VALUES('1','1','1');select*fromt2;INSERTINTO`t2` (`c2`, `c3`, `c4`)VALUES('1','1','1'); 结果: 结论...
1.对锁定表进行查看,修改 在session1中对t表加read锁,查看此时session1和session2对t表的读写情况。 可以看到,由于session1对t表加了read锁,所以session1和session2都可以读取t表数据,但是session1无法对t表进行写操作(增删改),session2对t表进行写操作则会陷入阻塞状态,除非session1执行"unlock tables"解锁操作,...
I am locking a table in mysql database by using: LOCK TABLE quantity WRITE; Even after locking it, I am able to insert data from mysql insert prompt and from my php application as well. Please correct me if I have done something wrong. ...
注意:如果使用LOCK TABLE WRITE锁定表后,则可以更新数据。详见后面介绍 复制 mysql>selectconnection_id();+---+| connection_id() |+---+| 61 |+---+1 rowinset(0.00 sec)mysql> showopentableswherein_use >=1;Emptyset(0.00 sec)mysql> lock tables testread;Query OK, 0rowsaffected (0.00 sec)...
mysql>LOCKTABLEtREAD;mysql>SELECT*FROMtASmyalias;ERROR 1100:Table 'myalias' was not locked with LOCK TABLES Conversely, if you lock a table using an alias, you must refer to it in your statements using that alias: mysql>LOCKTABLEtASmyaliasREAD;mysql>SELECT*FROMt;ERROR 1100:Table 't' was...
mysql lock table write MySQL中的表锁-写锁 在MySQL数据库中,表锁是一种用于控制并发访问的机制。其中,写锁是最严格的一种锁,用于保护正在被修改的数据。本文将介绍MySQL中的表锁-写锁的概念、使用场景以及示例代码。 概念 表锁是MySQL中最基本的一种锁。当对一个表进行写操作时,系统会自动为该表加上写锁...
mysql> showopentableswherein_use >0;+---+---+---+---+|Database|Table| In_use | Name_locked |+---+---+---+---+| MyDB | AO_60DB71_VERSION | 1 | 0 || MyDB | AO_AEFED0_TEAM_TO_MEMBER | 1 | 0 || MyDB | AO_4B00E6_STASH_SETTINGS | 1 | 0 || MyDB | AO_...
mysql> LOCK TABLE t READ; mysql> SELECT * FROM t AS myalias; ERROR 1100: Table 'myalias' was not locked with LOCK TABLES Conversely, if you lock a table using an alias, you must refer to it in your statements using that alias: mysql> LOCK TABLE t AS myalias READ; mysql> SELECT...
造成alter table产生Waiting for table metadata lock的原因其实很简单,一般是以下几个简单的场景: 场景一: 通过show processlist可以看到TableA上有正在进行的操作(包括读),此时alter table语句无法获取到metadata 独占锁,会进行等待。 这是最基本的一种情形,这个和mysql 5.6中的online ddl并不冲突。一般alter table的...
I am locking a table in mysql database by using: LOCK TABLE quantity WRITE; Even after locking it, I am able to insert data from mysql insert prompt and from my php application as well. Please correct me if I have done something wrong. ...