MySQL 5.7 自增字段相关参数说明

发布时间：2020-08-11 23:40:04 作者：feelpurple
来源：ITPUB博客阅读：204

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)

MySQL 5.7 自增字段相关参数说明

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