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auto_increment_increment 和 auto_increment_offset参数用在主主复制中,用于控制AUTO_INCREMENT字段的操作,在不同节点使用不同的生成规则,以避免生成的序列相同而产生冲突。 这两个参数可以分别设置全局和会话的变量,每个参数的值的范围是1~65535。将这两个参数设置为0会导致实际上将这两个参数的值设为1。 auto_increment_increment参数控制AUTO_INCREMENT字段值的间隔数 mysql> SHOW VARIABLES LIKE 'auto_inc%'; +--------------------------+-------+ | Variable_name | Value | +--------------------------+-------+ | auto_increment_increment | 1 | | auto_increment_offset | 1 | +--------------------------+-------+ 2 rows in set (0.00 sec) mysql> CREATE TABLE autoinc1 -> (col int not null auto_increment primary key) -> ; Query OK, 0 rows affected (0.12 sec) mysql> select @@auto_increment_increment; +----------------------------+ | @@auto_increment_increment | +----------------------------+ | 1 | +----------------------------+ 1 row in set (0.00 sec) mysql> set @@auto_increment_increment=10; Query OK, 0 rows affected (0.06 sec) mysql> select @@auto_increment_increment; +----------------------------+ | @@auto_increment_increment | +----------------------------+ | 10 | +----------------------------+ 1 row in set (0.00 sec) mysql> SHOW VARIABLES LIKE 'auto_inc%'; +--------------------------+-------+ | Variable_name | Value | +--------------------------+-------+ | auto_increment_increment | 10 | | auto_increment_offset | 1 | +--------------------------+-------+ 2 rows in set (0.00 sec) mysql> INSERT INTO autoinc1 VALUES(null),(null),(null); Query OK, 3 rows affected (0.00 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> SELECT col FROM autoinc1; +-----+ | col | +-----+ | 1 | | 11 | | 21 | +-----+ 3 rows in set (0.00 sec) auto_increment_offset 参数决定AUTO_INCREMENT字段的起始值 mysql> set @@auto_increment_offset=5; Query OK, 0 rows affected (0.00 sec) mysql> SHOW VARIABLES LIKE 'auto_inc%'; +--------------------------+-------+ | Variable_name | Value | +--------------------------+-------+ | auto_increment_increment | 10 | | auto_increment_offset | 5 | +--------------------------+-------+ 2 rows in set (0.00 sec) mysql> CREATE TABLE autoinc2 -> (col int not null auto_increment primary key); Query OK, 0 rows affected (0.64 sec) mysql> INSERT INTO autoinc2 VALUES (null),(null),(null); Query OK, 3 rows affected (0.00 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> SELECT col FROM autoinc2; +-----+ | col | +-----+ | 5 | | 15 | | 25 | +-----+ 3 rows in set (0.00 sec) 来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/26506993/viewspace-2098997/,如需转载,请注明出处,否则将追究法律责任。
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