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MySQL自增长的bug?

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;
MySQL自增长的bug?插图
MySQL自增长的bug?插图1

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

文章转载于:https://www.cnblogs.com/geaozhang/p/6837546.html

原著是一个有趣的人,若有侵权,请通知删除

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