实验环境:
mysql> status
————–
mysql Ver 14.14 Distrib 5.7.14, for Linux (x86_64) using EditLine wrapper……
mysql> show variables like 'auto_increment%';+--------------------------+-------+| Variable_name | Value |+--------------------------+-------+| auto_increment_increment | 1 || auto_increment_offset | 1 |+--------------------------+-------+2 rows in set (0.03 sec)
auto_increment_offset:默认自增长起始点值;
auto_increment_increment:默认自增长增量值;
(截图取材于标准MySQL5.7官方文档–没有盗版)
mysql> create table t1(id int not null primary key auto_increment);Query OK, 0 rows affected (0.21 sec)mysql> insert into t1 values(null),(null),(null);Query OK, 3 rows affected (0.06 sec)Records: 3 Duplicates: 0 Warnings: 0mysql> select * from t1;+----+| id |+----+| 1 || 2 || 3 |+----+3 rows in set (0.00 sec)
1、修改自增长变量值
mysql> set @@auto_increment_offset=10;Query OK, 0 rows affected (0.00 sec)mysql> set @@auto_increment_increment=5;Query OK, 0 rows affected (0.00 sec)mysql> show variables like 'auto_increment%';+--------------------------+-------+| Variable_name | Value |+--------------------------+-------+| auto_increment_increment | 5 || auto_increment_offset | 10 |+--------------------------+-------+2 rows in set (0.02 sec)
通过变量的修改,现在的自增长起始值是10,增量是5。
2、建表插值
mysql> create table t2(id int not null primary key auto_increment);Query OK, 0 rows affected (0.11 sec)mysql> insert into t2 values(null),(null),(null);Query OK, 3 rows affected (0.04 sec)Records: 3 Duplicates: 0 Warnings: 0
因为自增长起始值是10,增量是5;猜想结果值是10,15,20
3、查询结果
mysql> select * from t2;+----+| id |+----+| 4 || 9 || 10 |+----+3 rows in set (0.01 sec)
结果却非我们所猜想的???
继续插入值
mysql> insert into t2 values(null),(null),(null);Query OK, 3 rows affected (0.05 sec)Records: 3 Duplicates: 0 Warnings: 0mysql> select * from t2;+----+| id |+----+| 4 || 9 || 10 || 30 || 35 || 40 |+----+6 rows in set (0.00 sec)
经过多组测试,结果依旧(试验其他值都是正常的,唯独上述有问题)
那么,
问题来了,auto_increment_offset=10和auto_increment_increment=5这一组数值算是MySQL自增长里的一个bug吗?
评论前必须登录!
立即登录