Mysql锁之行级锁和表级意向锁

共享锁

排他锁

mysql>   begin;

Query OK, 0   rows affected (0.00 sec)

mysql>   SELECT * FROM t_compact WHERE c1 = 'a' FOR UPDATE;

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

| c1   | c2     | c3   |

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

| a    | aa     | aaa  |

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

1 row in set   (0.00 sec)

IS

IX

mysql> show create table t_compact\G

*************************** 1. row   ***************************

         Table: t_compact

Create Table: CREATE TABLE `t_compact` (

    `c1` varchar(10) NOT NULL,

    `c2` char(10) DEFAULT NULL,

    `c3` varchar(10) DEFAULT NULL,

    PRIMARY KEY (`c1`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

mysql> begin;

Query OK, 0 rows affected (0.00 sec)

mysql> select * FROM t_compact WHERE   c1 = 'a' FOR UPDATE;

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

| c1 | c2   | c3     |

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

| a    | aa   | aaa  |

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

1 row in set (0.00 sec)

mysql> begin;

Query OK, 0 rows affected (0.00 sec)

mysql> select * FROM t_compact WHERE   c1 = 'b' FOR UPDATE;

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

| c1 | c2   | c3     |

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

| b    | bb   | bbb  |

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

1 row in set (0.00 sec)

S

X

IS

IX